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 $94.69   7.760%   $102.0379   $102.04   $102.05   $102.00  
  Purchase #2 $192.96   6.865%   $206.2067   $206.21   $206.20   $206.20  
  Purchase #3 $111.77   8.804%   $121.6102   $121.61   $121.60   $121.60  
  Purchase #4 $68.40   5.462%   $72.136   $72.14   $72.15   $72.10  
  Purchase #5 $132.83   6.380%   $141.3046   $141.30   $141.30   $141.30  
  Purchase #6 $240.75   11.386%   $268.1618   $268.16   $268.15   $268.20  
  Purchase #7 $45.32   13.633%   $51.4985   $51.50   $51.50   $51.50  
  7 purchase totals = $886.72       $962.9557   $962.96   $962.95   $962.90