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 $95.36   6.282%   $101.3505   $101.35   $101.35   $101.40  
  Purchase #2 $215.34   8.413%   $233.4566   $233.46   $233.45   $233.50  
  Purchase #3 $64.68   3.529%   $66.9626   $66.96   $66.95   $67.00  
  Purchase #4 $68.37   5.195%   $71.9218   $71.92   $71.90   $71.90  
  Purchase #5 $148.28   4.194%   $154.4989   $154.50   $154.50   $154.50  
  Purchase #6 $245.71   11.478%   $273.9126   $273.91   $273.90   $273.90  
  Purchase #7 $45.25   8.127%   $48.9275   $48.93   $48.95   $48.90  
  7 purchase totals = $882.99       $951.0305   $951.03   $951.00   $951.10