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 $68.26   3.279%   $70.4982   $70.50   $70.50   $70.50  
  Purchase #2 $90.63   11.665%   $101.202   $101.20   $101.20   $101.20  
  Purchase #3 $217.91   7.373%   $233.9765   $233.98   $234.00   $234.00  
  Purchase #4 $59.69   7.710%   $64.2921   $64.29   $64.30   $64.30  
  Purchase #5 $171.54   5.134%   $180.3469   $180.35   $180.35   $180.30  
  Purchase #6 $211.52   11.742%   $236.3567   $236.36   $236.35   $236.40  
  Purchase #7 $60.28   10.484%   $66.5998   $66.60   $66.60   $66.60  
  7 purchase totals = $879.83       $953.2722   $953.28   $953.30   $953.30