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 $141.49   9.530%   $154.974   $154.97   $154.95   $155.00  
  Purchase #2 $244.40   3.852%   $253.8143   $253.81   $253.80   $253.80  
  Purchase #3 $113.82   12.873%   $128.472   $128.47   $128.45   $128.50  
  Purchase #4 $142.99   11.766%   $159.8142   $159.81   $159.80   $159.80  
  Purchase #5 $107.61   5.571%   $113.605   $113.61   $113.60   $113.60  
  Purchase #6 $250.93   4.246%   $261.5845   $261.58   $261.60   $261.60  
  Purchase #7 $29.98   13.259%   $33.955   $33.96   $33.95   $34.00  
  7 purchase totals = $1,031.22       $1,106.2190   $1,106.21   $1,106.15   $1,106.30