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 $194.98   7.495%   $209.5938   $209.59   $209.60   $209.60  
  Purchase #2 $85.82   10.837%   $95.1203   $95.12   $95.10   $95.10  
  Purchase #3 $71.29   3.105%   $73.5036   $73.50   $73.50   $73.50  
  Purchase #4 $127.49   11.683%   $142.3847   $142.38   $142.40   $142.40  
  Purchase #5 $32.81   5.786%   $34.7084   $34.71   $34.70   $34.70  
  Purchase #6 $129.52   4.204%   $134.965   $134.97   $134.95   $135.00  
  Purchase #7 $185.75   11.594%   $207.2859   $207.29   $207.30   $207.30  
  7 purchase totals = $827.66       $897.5617   $897.56   $897.55   $897.60