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 $60.95   6.475%   $64.8965   $64.90   $64.90   $64.90  
  Purchase #2 $147.78   4.281%   $154.1065   $154.11   $154.10   $154.10  
  Purchase #3 $10.61   5.134%   $11.1547   $11.15   $11.15   $11.20  
  Purchase #4 $85.65   11.633%   $95.6137   $95.61   $95.60   $95.60  
  Purchase #5 $110.92   13.371%   $125.7511   $125.75   $125.75   $125.80  
  Purchase #6 $205.61   4.630%   $215.1297   $215.13   $215.15   $215.10  
  Purchase #7 $55.53   6.384%   $59.075   $59.08   $59.10   $59.10  
  7 purchase totals = $677.05       $725.7272   $725.73   $725.75   $725.80