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 $119.63   6.113%   $126.943   $126.94   $126.95   $126.90  
  Purchase #2 $203.91   10.243%   $224.7965   $224.80   $224.80   $224.80  
  Purchase #3 $237.39   3.328%   $245.2903   $245.29   $245.30   $245.30  
  Purchase #4 $225.93   11.763%   $252.5061   $252.51   $252.50   $252.50  
  Purchase #5 $238.81   6.312%   $253.8837   $253.88   $253.90   $253.90  
  Purchase #6 $250.84   3.859%   $260.5199   $260.52   $260.50   $260.50  
  Purchase #7 $185.57   13.328%   $210.3028   $210.30   $210.30   $210.30  
  7 purchase totals = $1,462.08       $1,574.2423   $1,574.24   $1,574.25   $1,574.20