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 $66.54   13.602%   $75.5908   $75.59   $75.60   $75.60  
  Purchase #2 $147.59   5.199%   $155.2632   $155.26   $155.25   $155.30  
  Purchase #3 $92.73   11.149%   $103.0685   $103.07   $103.05   $103.10  
  Purchase #4 $244.46   11.282%   $272.04   $272.04   $272.05   $272.00  
  Purchase #5 $170.94   13.662%   $194.2938   $194.29   $194.30   $194.30  
  Purchase #6 $121.50   9.163%   $132.633   $132.63   $132.65   $132.60  
  Purchase #7 $226.54   7.552%   $243.6483   $243.65   $243.65   $243.60  
  7 purchase totals = $1,070.30       $1,176.5376   $1,176.53   $1,176.55   $1,176.50