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 $14.68   10.460%   $16.2155   $16.22   $16.20   $16.20  
  Purchase #2 $212.92   6.327%   $226.3914   $226.39   $226.40   $226.40  
  Purchase #3 $83.38   10.444%   $92.0882   $92.09   $92.10   $92.10  
  Purchase #4 $91.72   6.382%   $97.5736   $97.57   $97.55   $97.60  
  Purchase #5 $186.87   8.251%   $202.2886   $202.29   $202.30   $202.30  
  Purchase #6 $225.27   10.461%   $248.8355   $248.84   $248.85   $248.80  
  Purchase #7 $160.34   6.543%   $170.831   $170.83   $170.85   $170.80  
  7 purchase totals = $975.18       $1,054.2238   $1,054.23   $1,054.25   $1,054.20