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 $139.27   9.138%   $151.9965   $152.00   $152.00   $152.00  
  Purchase #2 $202.96   5.493%   $214.1086   $214.11   $214.10   $214.10  
  Purchase #3 $117.65   3.370%   $121.6148   $121.61   $121.60   $121.60  
  Purchase #4 $222.68   8.753%   $242.1712   $242.17   $242.15   $242.20  
  Purchase #5 $208.89   4.551%   $218.3966   $218.40   $218.40   $218.40  
  Purchase #6 $40.51   10.578%   $44.7951   $44.80   $44.80   $44.80  
  Purchase #7 $200.39   6.371%   $213.1568   $213.16   $213.15   $213.20  
  7 purchase totals = $1,132.35       $1,206.2396   $1,206.25   $1,206.20   $1,206.30