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 $214.30   13.867%   $244.017   $244.02   $244.00   $244.00  
  Purchase #2 $83.93   13.521%   $95.2782   $95.28   $95.30   $95.30  
  Purchase #3 $191.51   10.398%   $211.4232   $211.42   $211.40   $211.40  
  Purchase #4 $122.74   6.262%   $130.426   $130.43   $130.45   $130.40  
  Purchase #5 $141.50   13.221%   $160.2077   $160.21   $160.20   $160.20  
  Purchase #6 $74.95   13.786%   $85.2826   $85.28   $85.30   $85.30  
  Purchase #7 $125.33   13.485%   $142.2308   $142.23   $142.25   $142.20  
  7 purchase totals = $954.26       $1,068.8655   $1,068.87   $1,068.90   $1,068.80