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 $214.53   4.753%   $224.7266   $224.73   $224.75   $224.70  
  Purchase #2 $97.78   4.659%   $102.3356   $102.34   $102.35   $102.30  
  Purchase #3 $228.27   11.377%   $254.2403   $254.24   $254.25   $254.20  
  Purchase #4 $184.73   12.852%   $208.4715   $208.47   $208.45   $208.50  
  Purchase #5 $77.44   5.563%   $81.748   $81.75   $81.75   $81.70  
  Purchase #6 $203.65   6.225%   $216.3272   $216.33   $216.35   $216.30  
  Purchase #7 $112.57   5.598%   $118.8717   $118.87   $118.85   $118.90  
  7 purchase totals = $1,118.97       $1,206.7209   $1,206.73   $1,206.75   $1,206.60