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 $59.46   13.601%   $67.5472   $67.55   $67.55   $67.50  
  Purchase #2 $83.28   11.106%   $92.5291   $92.53   $92.55   $92.50  
  Purchase #3 $162.38   6.726%   $173.3017   $173.30   $173.30   $173.30  
  Purchase #4 $101.93   7.712%   $109.7908   $109.79   $109.80   $109.80  
  Purchase #5 $24.74   13.683%   $28.1252   $28.13   $28.15   $28.10  
  Purchase #6 $191.36   13.493%   $217.1802   $217.18   $217.20   $217.20  
  Purchase #7 $234.95   12.618%   $264.596   $264.60   $264.60   $264.60  
  7 purchase totals = $858.10       $953.0702   $953.08   $953.15   $953.00