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 $107.64   6.590%   $114.7335   $114.73   $114.75   $114.70  
  Purchase #2 $165.38   11.634%   $184.6203   $184.62   $184.60   $184.60  
  Purchase #3 $72.79   3.303%   $75.1943   $75.19   $75.20   $75.20  
  Purchase #4 $249.85   5.421%   $263.3944   $263.39   $263.40   $263.40  
  Purchase #5 $176.80   10.309%   $195.0263   $195.03   $195.05   $195.00  
  Purchase #6 $174.49   13.494%   $198.0357   $198.04   $198.05   $198.00  
  Purchase #7 $114.39   4.422%   $119.4483   $119.45   $119.45   $119.40  
  7 purchase totals = $1,061.34       $1,150.4528   $1,150.45   $1,150.50   $1,150.30