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 $57.36   3.306%   $59.2563   $59.26   $59.25   $59.30  
  Purchase #2 $215.52   10.203%   $237.5095   $237.51   $237.50   $237.50  
  Purchase #3 $5.49   4.848%   $5.7562   $5.76   $5.75   $5.80  
  Purchase #4 $201.46   5.652%   $212.8465   $212.85   $212.85   $212.80  
  Purchase #5 $214.69   6.531%   $228.7114   $228.71   $228.70   $228.70  
  Purchase #6 $231.29   12.499%   $260.1989   $260.20   $260.20   $260.20  
  Purchase #7 $219.66   13.442%   $249.1867   $249.19   $249.20   $249.20  
  7 purchase totals = $1,145.47       $1,253.4655   $1,253.48   $1,253.45   $1,253.50