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 $84.80   13.130%   $95.9342   $95.93   $95.95   $95.90  
  Purchase #2 $230.61   11.122%   $256.2584   $256.26   $256.25   $256.30  
  Purchase #3 $147.87   3.620%   $153.2229   $153.22   $153.20   $153.20  
  Purchase #4 $245.87   8.482%   $266.7247   $266.72   $266.70   $266.70  
  Purchase #5 $146.30   12.107%   $164.0125   $164.01   $164.00   $164.00  
  Purchase #6 $13.77   3.554%   $14.2594   $14.26   $14.25   $14.30  
  Purchase #7 $99.73   3.661%   $103.3811   $103.38   $103.40   $103.40  
  7 purchase totals = $968.95       $1,053.7932   $1,053.78   $1,053.75   $1,053.80