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 $162.94   6.765%   $173.9629   $173.96   $173.95   $174.00  
  Purchase #2 $89.67   3.105%   $92.4543   $92.45   $92.45   $92.50  
  Purchase #3 $219.49   11.258%   $244.2002   $244.20   $244.20   $244.20  
  Purchase #4 $242.26   13.651%   $275.3309   $275.33   $275.35   $275.30  
  Purchase #5 $129.57   11.339%   $144.2619   $144.26   $144.25   $144.30  
  Purchase #6 $17.78   6.642%   $18.9609   $18.96   $18.95   $19.00  
  Purchase #7 $196.70   10.814%   $217.9711   $217.97   $217.95   $218.00  
  7 purchase totals = $1,058.41       $1,167.1422   $1,167.13   $1,167.10   $1,167.30