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 $95.36   6.467%   $101.5269   $101.53   $101.55   $101.50  
  Purchase #2 $158.40   10.860%   $175.6022   $175.60   $175.60   $175.60  
  Purchase #3 $248.56   10.634%   $274.9919   $274.99   $275.00   $275.00  
  Purchase #4 $73.42   8.694%   $79.8031   $79.80   $79.80   $79.80  
  Purchase #5 $28.96   13.754%   $32.9432   $32.94   $32.95   $32.90  
  Purchase #6 $10.49   8.466%   $11.3781   $11.38   $11.40   $11.40  
  Purchase #7 $184.50   11.471%   $205.664   $205.66   $205.65   $205.70  
  7 purchase totals = $799.69       $881.9094   $881.90   $881.95   $881.90