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 $118.82   5.744%   $125.645   $125.65   $125.65   $125.60  
  Purchase #2 $36.33   3.237%   $37.506   $37.51   $37.50   $37.50  
  Purchase #3 $28.60   4.206%   $29.8029   $29.80   $29.80   $29.80  
  Purchase #4 $213.62   10.698%   $236.4731   $236.47   $236.45   $236.50  
  Purchase #5 $221.96   8.358%   $240.5114   $240.51   $240.50   $240.50  
  Purchase #6 $57.60   3.581%   $59.6627   $59.66   $59.65   $59.70  
  Purchase #7 $204.66   10.822%   $226.8083   $226.81   $226.80   $226.80  
  7 purchase totals = $881.59       $956.4094   $956.41   $956.35   $956.40