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 $191.42   7.602%   $205.9717   $205.97   $205.95   $206.00  
  Purchase #2 $60.35   10.847%   $66.8962   $66.90   $66.90   $66.90  
  Purchase #3 $69.28   6.420%   $73.7278   $73.73   $73.75   $73.70  
  Purchase #4 $218.80   6.370%   $232.7376   $232.74   $232.75   $232.70  
  Purchase #5 $188.42   4.614%   $197.1137   $197.11   $197.10   $197.10  
  Purchase #6 $88.49   12.536%   $99.5831   $99.58   $99.60   $99.60  
  Purchase #7 $89.44   4.196%   $93.1929   $93.19   $93.20   $93.20  
  7 purchase totals = $906.20       $969.2230   $969.22   $969.25   $969.20