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 $66.74   9.754%   $73.2498   $73.25   $73.25   $73.20  
  Purchase #2 $118.94   6.485%   $126.6533   $126.65   $126.65   $126.70  
  Purchase #3 $111.76   3.670%   $115.8616   $115.86   $115.85   $115.90  
  Purchase #4 $233.76   3.367%   $241.6307   $241.63   $241.65   $241.60  
  Purchase #5 $221.36   5.708%   $233.9952   $234.00   $234.00   $234.00  
  Purchase #6 $56.26   11.759%   $62.8756   $62.88   $62.90   $62.90  
  Purchase #7 $213.61   8.504%   $231.7754   $231.78   $231.80   $231.80  
  7 purchase totals = $1,022.43       $1,086.0416   $1,086.05   $1,086.10   $1,086.10