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 $58.49   7.371%   $62.8013   $62.80   $62.80   $62.80  
  Purchase #2 $200.92   6.106%   $213.1882   $213.19   $213.20   $213.20  
  Purchase #3 $166.57   10.804%   $184.5662   $184.57   $184.55   $184.60  
  Purchase #4 $142.91   7.584%   $153.7483   $153.75   $153.75   $153.70  
  Purchase #5 $115.85   6.694%   $123.605   $123.61   $123.60   $123.60  
  Purchase #6 $164.79   11.504%   $183.7474   $183.75   $183.75   $183.70  
  Purchase #7 $82.66   4.151%   $86.0912   $86.09   $86.10   $86.10  
  7 purchase totals = $932.19       $1,007.7476   $1,007.76   $1,007.75   $1,007.70