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 $182.38   10.563%   $201.6448   $201.64   $201.65   $201.60  
  Purchase #2 $217.65   8.399%   $235.9304   $235.93   $235.95   $235.90  
  Purchase #3 $99.51   13.394%   $112.8384   $112.84   $112.85   $112.80  
  Purchase #4 $146.68   8.588%   $159.2769   $159.28   $159.30   $159.30  
  Purchase #5 $180.51   5.834%   $191.041   $191.04   $191.05   $191.00  
  Purchase #6 $103.50   8.815%   $112.6235   $112.62   $112.60   $112.60  
  Purchase #7 $85.88   4.697%   $89.9138   $89.91   $89.90   $89.90  
  7 purchase totals = $1,016.11       $1,103.2688   $1,103.26   $1,103.30   $1,103.10