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 $209.55   4.357%   $218.6801   $218.68   $218.70   $218.70  
  Purchase #2 $250.63   13.429%   $284.2871   $284.29   $284.30   $284.30  
  Purchase #3 $55.78   9.612%   $61.1416   $61.14   $61.15   $61.10  
  Purchase #4 $227.93   6.152%   $241.9523   $241.95   $241.95   $242.00  
  Purchase #5 $145.85   5.131%   $153.3336   $153.33   $153.35   $153.30  
  Purchase #6 $12.36   10.541%   $13.6629   $13.66   $13.65   $13.70  
  Purchase #7 $57.96   3.559%   $60.0228   $60.02   $60.00   $60.00  
  7 purchase totals = $960.06       $1,033.0804   $1,033.07   $1,033.10   $1,033.10