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 $59.56   10.708%   $65.9377   $65.94   $65.95   $65.90  
  Purchase #2 $172.70   11.161%   $191.975   $191.98   $192.00   $192.00  
  Purchase #3 $16.95   11.562%   $18.9098   $18.91   $18.90   $18.90  
  Purchase #4 $207.51   4.755%   $217.3771   $217.38   $217.40   $217.40  
  Purchase #5 $106.79   6.617%   $113.8563   $113.86   $113.85   $113.90  
  Purchase #6 $195.54   9.180%   $213.4906   $213.49   $213.50   $213.50  
  Purchase #7 $152.25   5.597%   $160.7714   $160.77   $160.75   $160.80  
  7 purchase totals = $911.30       $982.3179   $982.33   $982.35   $982.40