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 $119.56   6.172%   $126.9392   $126.94   $126.95   $126.90  
  Purchase #2 $233.73   12.469%   $262.8738   $262.87   $262.85   $262.90  
  Purchase #3 $215.30   6.263%   $228.7842   $228.78   $228.80   $228.80  
  Purchase #4 $231.80   8.185%   $250.7728   $250.77   $250.75   $250.80  
  Purchase #5 $22.39   7.390%   $24.0446   $24.04   $24.05   $24.00  
  Purchase #6 $215.73   8.192%   $233.4026   $233.40   $233.40   $233.40  
  Purchase #7 $144.43   10.369%   $159.4059   $159.41   $159.40   $159.40  
  7 purchase totals = $1,182.94       $1,286.2231   $1,286.21   $1,286.20   $1,286.20