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 $95.61   5.758%   $101.1152   $101.12   $101.10   $101.10  
  Purchase #2 $50.53   4.811%   $52.961   $52.96   $52.95   $53.00  
  Purchase #3 $77.93   10.287%   $85.9467   $85.95   $85.95   $85.90  
  Purchase #4 $35.30   13.169%   $39.9487   $39.95   $39.95   $39.90  
  Purchase #5 $217.66   3.406%   $225.0735   $225.07   $225.05   $225.10  
  Purchase #6 $242.80   7.745%   $261.6049   $261.60   $261.60   $261.60  
  Purchase #7 $183.41   8.404%   $198.8238   $198.82   $198.80   $198.80  
  7 purchase totals = $903.24       $965.4738   $965.47   $965.40   $965.40