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 $69.38   10.473%   $76.6462   $76.65   $76.65   $76.60  
  Purchase #2 $126.73   9.181%   $138.3651   $138.37   $138.35   $138.40  
  Purchase #3 $119.80   3.812%   $124.3668   $124.37   $124.35   $124.40  
  Purchase #4 $126.87   3.356%   $131.1278   $131.13   $131.15   $131.10  
  Purchase #5 $19.32   6.600%   $20.5951   $20.60   $20.60   $20.60  
  Purchase #6 $216.76   11.381%   $241.4295   $241.43   $241.45   $241.40  
  Purchase #7 $16.86   10.539%   $18.6369   $18.64   $18.65   $18.60  
  7 purchase totals = $695.72       $751.1674   $751.19   $751.20   $751.10