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 $92.81   3.750%   $96.2904   $96.29   $96.30   $96.30  
  Purchase #2 $141.48   5.145%   $148.7591   $148.76   $148.75   $148.80  
  Purchase #3 $173.61   9.466%   $190.0439   $190.04   $190.05   $190.00  
  Purchase #4 $52.75   12.244%   $59.2087   $59.21   $59.20   $59.20  
  Purchase #5 $243.69   7.210%   $261.26   $261.26   $261.25   $261.30  
  Purchase #6 $93.26   3.171%   $96.2173   $96.22   $96.20   $96.20  
  Purchase #7 $250.64   12.863%   $282.8798   $282.88   $282.90   $282.90  
  7 purchase totals = $1,048.24       $1,134.6592   $1,134.66   $1,134.65   $1,134.70