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 $192.76   11.122%   $214.1988   $214.20   $214.20   $214.20  
  Purchase #2 $23.53   5.470%   $24.8171   $24.82   $24.80   $24.80  
  Purchase #3 $152.58   5.634%   $161.1764   $161.18   $161.20   $161.20  
  Purchase #4 $183.38   13.382%   $207.9199   $207.92   $207.90   $207.90  
  Purchase #5 $192.99   3.739%   $200.2059   $200.21   $200.20   $200.20  
  Purchase #6 $141.99   3.170%   $146.4911   $146.49   $146.50   $146.50  
  Purchase #7 $186.39   13.746%   $212.0112   $212.01   $212.00   $212.00  
  7 purchase totals = $1,073.62       $1,166.8204   $1,166.83   $1,166.80   $1,166.80