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 $176.72   11.828%   $197.6224   $197.62   $197.60   $197.60  
  Purchase #2 $191.26   8.778%   $208.0488   $208.05   $208.05   $208.00  
  Purchase #3 $244.75   9.815%   $268.7722   $268.77   $268.75   $268.80  
  Purchase #4 $182.81   4.854%   $191.6836   $191.68   $191.70   $191.70  
  Purchase #5 $174.41   4.760%   $182.7119   $182.71   $182.70   $182.70  
  Purchase #6 $146.93   13.176%   $166.2895   $166.29   $166.30   $166.30  
  Purchase #7 $210.38   4.389%   $219.6136   $219.61   $219.60   $219.60  
  7 purchase totals = $1,327.26       $1,434.7420   $1,434.73   $1,434.70   $1,434.70