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 $56.46   5.203%   $59.3976   $59.40   $59.40   $59.40  
  Purchase #2 $110.63   6.183%   $117.4703   $117.47   $117.45   $117.50  
  Purchase #3 $245.95   3.406%   $254.3271   $254.33   $254.35   $254.30  
  Purchase #4 $55.50   5.743%   $58.6874   $58.69   $58.70   $58.70  
  Purchase #5 $106.58   8.498%   $115.6372   $115.64   $115.65   $115.60  
  Purchase #6 $194.84   5.853%   $206.244   $206.24   $206.25   $206.20  
  Purchase #7 $131.86   7.126%   $141.2563   $141.26   $141.25   $141.30  
  7 purchase totals = $901.82       $953.0199   $953.03   $953.05   $953.00