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 $58.44   7.270%   $62.6886   $62.69   $62.70   $62.70  
  Purchase #2 $234.82   11.739%   $262.3855   $262.39   $262.40   $262.40  
  Purchase #3 $237.28   10.163%   $261.3948   $261.39   $261.40   $261.40  
  Purchase #4 $126.67   11.278%   $140.9558   $140.96   $140.95   $141.00  
  Purchase #5 $231.34   12.575%   $260.431   $260.43   $260.45   $260.40  
  Purchase #6 $204.96   4.164%   $213.4945   $213.49   $213.50   $213.50  
  Purchase #7 $98.28   3.786%   $102.0009   $102.00   $102.00   $102.00  
  7 purchase totals = $1,191.79       $1,303.3511   $1,303.35   $1,303.40   $1,303.40