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 $204.94   8.305%   $221.9603   $221.96   $221.95   $222.00  
  Purchase #2 $170.51   7.505%   $183.3068   $183.31   $183.30   $183.30  
  Purchase #3 $22.39   4.321%   $23.3575   $23.36   $23.35   $23.40  
  Purchase #4 $5.68   3.166%   $5.8598   $5.86   $5.85   $5.90  
  Purchase #5 $184.85   8.268%   $200.1334   $200.13   $200.15   $200.10  
  Purchase #6 $192.84   11.706%   $215.4139   $215.41   $215.40   $215.40  
  Purchase #7 $94.95   7.473%   $102.0456   $102.05   $102.05   $102.00  
  7 purchase totals = $876.16       $952.0773   $952.08   $952.05   $952.10