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 $65.55   11.872%   $73.3321   $73.33   $73.35   $73.30  
  Purchase #2 $158.49   12.800%   $178.7767   $178.78   $178.80   $178.80  
  Purchase #3 $10.54   10.581%   $11.6552   $11.66   $11.65   $11.70  
  Purchase #4 $199.66   3.871%   $207.3888   $207.39   $207.40   $207.40  
  Purchase #5 $230.70   9.750%   $253.1933   $253.19   $253.20   $253.20  
  Purchase #6 $64.32   11.599%   $71.7805   $71.78   $71.80   $71.80  
  Purchase #7 $203.81   12.254%   $228.7849   $228.78   $228.80   $228.80  
  7 purchase totals = $933.07       $1,024.9115   $1,024.91   $1,025.00   $1,025.00