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 $215.32   13.608%   $244.6207   $244.62   $244.60   $244.60  
  Purchase #2 $208.80   4.815%   $218.8537   $218.85   $218.85   $218.90  
  Purchase #3 $153.72   3.191%   $158.6252   $158.63   $158.65   $158.60  
  Purchase #4 $134.29   13.293%   $152.1412   $152.14   $152.15   $152.10  
  Purchase #5 $233.64   13.636%   $265.4992   $265.50   $265.50   $265.50  
  Purchase #6 $130.79   12.507%   $147.1479   $147.15   $147.15   $147.10  
  Purchase #7 $173.92   7.322%   $186.6544   $186.65   $186.65   $186.70  
  7 purchase totals = $1,250.48       $1,373.5423   $1,373.54   $1,373.55   $1,373.50