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 $208.85   11.779%   $233.4504   $233.45   $233.45   $233.50  
  Purchase #2 $195.26   9.145%   $213.1165   $213.12   $213.10   $213.10  
  Purchase #3 $67.87   5.726%   $71.7562   $71.76   $71.75   $71.80  
  Purchase #4 $57.66   4.808%   $60.4323   $60.43   $60.45   $60.40  
  Purchase #5 $199.49   13.553%   $226.5269   $226.53   $226.55   $226.50  
  Purchase #6 $71.50   7.732%   $77.0284   $77.03   $77.05   $77.00  
  Purchase #7 $195.48   5.407%   $206.0496   $206.05   $206.05   $206.00  
  7 purchase totals = $996.11       $1,088.3603   $1,088.37   $1,088.40   $1,088.30