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 $88.29   4.828%   $92.5526   $92.55   $92.55   $92.60  
  Purchase #2 $115.28   10.817%   $127.7498   $127.75   $127.75   $127.70  
  Purchase #3 $216.39   11.577%   $241.4415   $241.44   $241.45   $241.40  
  Purchase #4 $30.36   10.208%   $33.4591   $33.46   $33.45   $33.50  
  Purchase #5 $5.82   11.276%   $6.4763   $6.48   $6.50   $6.50  
  Purchase #6 $112.37   10.547%   $124.2217   $124.22   $124.20   $124.20  
  Purchase #7 $221.52   13.779%   $252.0432   $252.04   $252.05   $252.00  
  7 purchase totals = $790.03       $877.9442   $877.94   $877.95   $877.90