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 $86.61   10.266%   $95.5014   $95.50   $95.50   $95.50  
  Purchase #2 $151.56   11.720%   $169.3228   $169.32   $169.30   $169.30  
  Purchase #3 $133.38   12.662%   $150.2686   $150.27   $150.25   $150.30  
  Purchase #4 $149.25   3.281%   $154.1469   $154.15   $154.15   $154.10  
  Purchase #5 $64.35   7.671%   $69.2863   $69.29   $69.30   $69.30  
  Purchase #6 $118.82   3.345%   $122.7945   $122.79   $122.80   $122.80  
  Purchase #7 $189.50   6.584%   $201.9767   $201.98   $202.00   $202.00  
  7 purchase totals = $893.47       $963.2972   $963.30   $963.30   $963.30