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 $44.81   6.243%   $47.6075   $47.61   $47.60   $47.60  
  Purchase #2 $87.78   5.604%   $92.6992   $92.70   $92.70   $92.70  
  Purchase #3 $59.78   11.558%   $66.6894   $66.69   $66.70   $66.70  
  Purchase #4 $204.58   10.426%   $225.9095   $225.91   $225.90   $225.90  
  Purchase #5 $121.51   4.411%   $126.8698   $126.87   $126.85   $126.90  
  Purchase #6 $229.84   11.614%   $256.5336   $256.53   $256.55   $256.50  
  Purchase #7 $7.96   11.548%   $8.8792   $8.88   $8.90   $8.90  
  7 purchase totals = $756.26       $825.1882   $825.19   $825.20   $825.20