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 $86.86   10.587%   $96.0559   $96.06   $96.05   $96.10  
  Purchase #2 $74.92   6.162%   $79.5366   $79.54   $79.55   $79.50  
  Purchase #3 $45.64   5.105%   $47.9699   $47.97   $47.95   $48.00  
  Purchase #4 $132.88   3.467%   $137.4869   $137.49   $137.50   $137.50  
  Purchase #5 $182.33   13.394%   $206.7513   $206.75   $206.75   $206.80  
  Purchase #6 $128.51   3.811%   $133.4075   $133.41   $133.40   $133.40  
  Purchase #7 $50.29   7.664%   $54.1442   $54.14   $54.15   $54.10  
  7 purchase totals = $701.43       $755.3523   $755.36   $755.35   $755.40