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 $60.26   12.388%   $67.725   $67.73   $67.75   $67.70  
  Purchase #2 $141.38   10.307%   $155.952   $155.95   $155.95   $156.00  
  Purchase #3 $63.71   6.700%   $67.9786   $67.98   $68.00   $68.00  
  Purchase #4 $97.93   4.487%   $102.3241   $102.32   $102.30   $102.30  
  Purchase #5 $127.31   10.353%   $140.4904   $140.49   $140.50   $140.50  
  Purchase #6 $164.27   5.276%   $172.9369   $172.94   $172.95   $172.90  
  Purchase #7 $158.36   7.289%   $169.9029   $169.90   $169.90   $169.90  
  7 purchase totals = $813.22       $877.3099   $877.31   $877.35   $877.30