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 $219.81   10.369%   $242.6021   $242.60   $242.60   $242.60  
  Purchase #2 $17.57   9.482%   $19.236   $19.24   $19.25   $19.20  
  Purchase #3 $9.55   11.317%   $10.6308   $10.63   $10.65   $10.60  
  Purchase #4 $215.91   13.142%   $244.2849   $244.28   $244.30   $244.30  
  Purchase #5 $91.70   4.426%   $95.7586   $95.76   $95.75   $95.80  
  Purchase #6 $123.83   8.118%   $133.8825   $133.88   $133.90   $133.90  
  Purchase #7 $183.35   13.618%   $208.3186   $208.32   $208.30   $208.30  
  7 purchase totals = $861.72       $954.7135   $954.71   $954.75   $954.70