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 $59.67   7.166%   $63.946   $63.95   $63.95   $63.90  
  Purchase #2 $22.43   7.586%   $24.1315   $24.13   $24.15   $24.10  
  Purchase #3 $95.49   12.108%   $107.0519   $107.05   $107.05   $107.10  
  Purchase #4 $63.99   5.777%   $67.6867   $67.69   $67.70   $67.70  
  Purchase #5 $84.46   11.204%   $93.9229   $93.92   $93.90   $93.90  
  Purchase #6 $142.85   9.756%   $156.7864   $156.79   $156.80   $156.80  
  Purchase #7 $137.76   9.187%   $150.416   $150.42   $150.40   $150.40  
  7 purchase totals = $606.65       $663.9414   $663.95   $663.95   $663.90