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 $42.61   3.171%   $43.9612   $43.96   $43.95   $44.00  
  Purchase #2 $200.27   10.743%   $221.785   $221.79   $221.80   $221.80  
  Purchase #3 $106.68   11.213%   $118.642   $118.64   $118.65   $118.60  
  Purchase #4 $242.73   5.191%   $255.3301   $255.33   $255.35   $255.30  
  Purchase #5 $204.62   10.757%   $226.631   $226.63   $226.65   $226.60  
  Purchase #6 $140.49   12.249%   $157.6986   $157.70   $157.70   $157.70  
  Purchase #7 $190.50   6.815%   $203.4826   $203.48   $203.50   $203.50  
  7 purchase totals = $1,127.90       $1,227.5305   $1,227.53   $1,227.60   $1,227.50