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 $41.90   5.148%   $44.057   $44.06   $44.05   $44.10  
  Purchase #2 $249.67   10.795%   $276.6219   $276.62   $276.60   $276.60  
  Purchase #3 $55.59   13.749%   $63.2331   $63.23   $63.25   $63.20  
  Purchase #4 $118.93   4.387%   $124.1475   $124.15   $124.15   $124.10  
  Purchase #5 $178.76   6.431%   $190.2561   $190.26   $190.25   $190.30  
  Purchase #6 $54.47   4.427%   $56.8814   $56.88   $56.90   $56.90  
  Purchase #7 $132.96   5.309%   $140.0188   $140.02   $140.00   $140.00  
  7 purchase totals = $832.28       $895.2158   $895.22   $895.20   $895.20