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 $232.34   3.559%   $240.609   $240.61   $240.60   $240.60  
  Purchase #2 $245.58   8.157%   $265.612   $265.61   $265.60   $265.60  
  Purchase #3 $175.33   10.532%   $193.7958   $193.80   $193.80   $193.80  
  Purchase #4 $91.67   10.794%   $101.5649   $101.56   $101.55   $101.60  
  Purchase #5 $224.45   11.697%   $250.7039   $250.70   $250.70   $250.70  
  Purchase #6 $119.43   3.457%   $123.5587   $123.56   $123.55   $123.60  
  Purchase #7 $218.27   9.448%   $238.8921   $238.89   $238.90   $238.90  
  7 purchase totals = $1,307.07       $1,414.7364   $1,414.73   $1,414.70   $1,414.80