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 $44.44   6.531%   $47.3424   $47.34   $47.35   $47.30  
  Purchase #2 $244.73   8.371%   $265.2163   $265.22   $265.20   $265.20  
  Purchase #3 $204.67   11.422%   $228.0474   $228.05   $228.05   $228.00  
  Purchase #4 $81.43   4.736%   $85.2865   $85.29   $85.30   $85.30  
  Purchase #5 $201.43   6.508%   $214.5391   $214.54   $214.55   $214.50  
  Purchase #6 $102.44   7.472%   $110.0943   $110.09   $110.10   $110.10  
  Purchase #7 $224.71   11.521%   $250.5988   $250.60   $250.60   $250.60  
  7 purchase totals = $1,103.85       $1,201.1248   $1,201.13   $1,201.15   $1,201.00