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 $43.90   5.213%   $46.1885   $46.19   $46.20   $46.20  
  Purchase #2 $133.73   12.620%   $150.6067   $150.61   $150.60   $150.60  
  Purchase #3 $99.38   13.440%   $112.7367   $112.74   $112.75   $112.70  
  Purchase #4 $230.67   11.128%   $256.339   $256.34   $256.35   $256.30  
  Purchase #5 $247.66   9.529%   $271.2595   $271.26   $271.25   $271.30  
  Purchase #6 $249.28   10.723%   $276.0103   $276.01   $276.00   $276.00  
  Purchase #7 $144.76   13.243%   $163.9306   $163.93   $163.95   $163.90  
  7 purchase totals = $1,149.38       $1,277.0713   $1,277.08   $1,277.10   $1,277.00