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 $222.53   8.373%   $241.1624   $241.16   $241.15   $241.20  
  Purchase #2 $151.79   3.709%   $157.4199   $157.42   $157.40   $157.40  
  Purchase #3 $146.99   9.515%   $160.9761   $160.98   $161.00   $161.00  
  Purchase #4 $154.56   5.864%   $163.6234   $163.62   $163.60   $163.60  
  Purchase #5 $51.35   3.218%   $53.0024   $53.00   $53.00   $53.00  
  Purchase #6 $131.95   3.688%   $136.8163   $136.82   $136.80   $136.80  
  Purchase #7 $205.26   13.770%   $233.5243   $233.52   $233.50   $233.50  
  7 purchase totals = $1,064.43       $1,146.5248   $1,146.52   $1,146.45   $1,146.50