Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $113.34   12.870%   $127.9269   $127.93   $127.95   $127.90  
  Purchase #2 $176.64   10.644%   $195.4416   $195.44   $195.45   $195.40  
  Purchase #3 $186.37   8.524%   $202.2562   $202.26   $202.25   $202.30  
  Purchase #4 $211.65   10.671%   $234.2352   $234.24   $234.25   $234.20  
  Purchase #5 $213.51   11.277%   $237.5875   $237.59   $237.60   $237.60  
  Purchase #6 $158.80   11.683%   $177.3526   $177.35   $177.35   $177.40  
  Purchase #7 $180.74   11.554%   $201.6227   $201.62   $201.60   $201.60  
  7 purchase totals = $1,241.05       $1,376.4227   $1,376.43   $1,376.45   $1,376.40