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 $207.94   4.219%   $216.713   $216.71   $216.70   $216.70  
  Purchase #2 $245.79   11.495%   $274.0436   $274.04   $274.05   $274.00  
  Purchase #3 $119.85   10.743%   $132.7255   $132.73   $132.75   $132.70  
  Purchase #4 $169.76   4.140%   $176.7881   $176.79   $176.80   $176.80  
  Purchase #5 $157.38   6.839%   $168.1432   $168.14   $168.15   $168.10  
  Purchase #6 $51.38   8.798%   $55.9004   $55.90   $55.90   $55.90  
  Purchase #7 $87.94   7.164%   $94.24   $94.24   $94.25   $94.20  
  7 purchase totals = $1,040.04       $1,118.5538   $1,118.55   $1,118.60   $1,118.40