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 $174.33   11.852%   $194.9916   $194.99   $195.00   $195.00  
  Purchase #2 $132.94   3.588%   $137.7099   $137.71   $137.70   $137.70  
  Purchase #3 $201.39   6.105%   $213.6849   $213.68   $213.70   $213.70  
  Purchase #4 $102.43   13.133%   $115.8821   $115.88   $115.90   $115.90  
  Purchase #5 $144.94   6.424%   $154.2509   $154.25   $154.25   $154.30  
  Purchase #6 $203.87   6.559%   $217.2418   $217.24   $217.25   $217.20  
  Purchase #7 $152.76   12.266%   $171.4975   $171.50   $171.50   $171.50  
  7 purchase totals = $1,112.66       $1,205.2587   $1,205.25   $1,205.30   $1,205.30