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 $46.84   9.264%   $51.1793   $51.18   $51.20   $51.20  
  Purchase #2 $246.50   3.219%   $254.4348   $254.43   $254.45   $254.40  
  Purchase #3 $243.49   7.435%   $261.5935   $261.59   $261.60   $261.60  
  Purchase #4 $185.36   7.739%   $199.705   $199.71   $199.70   $199.70  
  Purchase #5 $209.35   7.633%   $225.3297   $225.33   $225.35   $225.30  
  Purchase #6 $230.62   11.199%   $256.4471   $256.45   $256.45   $256.40  
  Purchase #7 $215.53   9.796%   $236.6433   $236.64   $236.65   $236.60  
  7 purchase totals = $1,377.69       $1,485.3327   $1,485.33   $1,485.40   $1,485.20