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 $95.95   11.719%   $107.1944   $107.19   $107.20   $107.20  
  Purchase #2 $149.91   13.804%   $170.6036   $170.60   $170.60   $170.60  
  Purchase #3 $112.50   8.122%   $121.6373   $121.64   $121.65   $121.60  
  Purchase #4 $98.44   9.642%   $107.9316   $107.93   $107.95   $107.90  
  Purchase #5 $145.27   5.395%   $153.1073   $153.11   $153.10   $153.10  
  Purchase #6 $232.43   10.271%   $256.3029   $256.30   $256.30   $256.30  
  Purchase #7 $134.85   5.657%   $142.4785   $142.48   $142.50   $142.50  
  7 purchase totals = $969.35       $1,059.2556   $1,059.25   $1,059.30   $1,059.20