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 $209.71   13.306%   $237.614   $237.61   $237.60   $237.60  
  Purchase #2 $235.55   11.540%   $262.7325   $262.73   $262.75   $262.70  
  Purchase #3 $222.65   13.733%   $253.2265   $253.23   $253.25   $253.20  
  Purchase #4 $241.58   13.148%   $273.3429   $273.34   $273.35   $273.30  
  Purchase #5 $60.52   7.591%   $65.1141   $65.11   $65.10   $65.10  
  Purchase #6 $153.28   3.215%   $158.208   $158.21   $158.20   $158.20  
  Purchase #7 $216.38   3.119%   $223.1289   $223.13   $223.15   $223.10  
  7 purchase totals = $1,339.67       $1,473.3669   $1,473.36   $1,473.40   $1,473.20