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 $82.76   4.381%   $86.3857   $86.39   $86.40   $86.40  
  Purchase #2 $195.65   10.733%   $216.6491   $216.65   $216.65   $216.60  
  Purchase #3 $118.59   6.551%   $126.3588   $126.36   $126.35   $126.40  
  Purchase #4 $60.82   8.557%   $66.0244   $66.02   $66.00   $66.00  
  Purchase #5 $143.46   5.374%   $151.1695   $151.17   $151.15   $151.20  
  Purchase #6 $74.51   3.561%   $77.1633   $77.16   $77.15   $77.20  
  Purchase #7 $11.32   11.357%   $12.6056   $12.61   $12.60   $12.60  
  7 purchase totals = $687.11       $736.3564   $736.36   $736.30   $736.40