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 $146.54   3.709%   $151.9752   $151.98   $152.00   $152.00  
  Purchase #2 $103.62   8.472%   $112.3987   $112.40   $112.40   $112.40  
  Purchase #3 $41.88   3.600%   $43.3877   $43.39   $43.40   $43.40  
  Purchase #4 $200.93   4.262%   $209.4936   $209.49   $209.50   $209.50  
  Purchase #5 $124.27   12.189%   $139.4173   $139.42   $139.40   $139.40  
  Purchase #6 $179.29   13.838%   $204.1002   $204.10   $204.10   $204.10  
  Purchase #7 $237.74   6.383%   $252.9149   $252.91   $252.90   $252.90  
  7 purchase totals = $1,034.27       $1,113.6876   $1,113.69   $1,113.70   $1,113.70