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 $114.66   3.697%   $118.899   $118.90   $118.90   $118.90  
  Purchase #2 $242.78   7.258%   $260.401   $260.40   $260.40   $260.40  
  Purchase #3 $212.42   4.141%   $221.2163   $221.22   $221.20   $221.20  
  Purchase #4 $12.32   12.219%   $13.8254   $13.83   $13.85   $13.80  
  Purchase #5 $161.91   5.292%   $170.4783   $170.48   $170.50   $170.50  
  Purchase #6 $239.57   3.372%   $247.6483   $247.65   $247.65   $247.60  
  Purchase #7 $212.96   6.718%   $227.2667   $227.27   $227.25   $227.30  
  7 purchase totals = $1,196.62       $1,259.7350   $1,259.75   $1,259.75   $1,259.70