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 $63.60   13.717%   $72.324   $72.32   $72.30   $72.30  
  Purchase #2 $239.92   10.171%   $264.3223   $264.32   $264.30   $264.30  
  Purchase #3 $56.73   10.391%   $62.6248   $62.62   $62.60   $62.60  
  Purchase #4 $24.88   12.452%   $27.9781   $27.98   $28.00   $28.00  
  Purchase #5 $14.65   8.756%   $15.9328   $15.93   $15.95   $15.90  
  Purchase #6 $211.33   12.127%   $236.958   $236.96   $236.95   $237.00  
  Purchase #7 $195.71   12.655%   $220.4771   $220.48   $220.50   $220.50  
  7 purchase totals = $806.82       $900.6171   $900.61   $900.60   $900.60