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 $97.59   7.203%   $104.6194   $104.62   $104.60   $104.60  
  Purchase #2 $238.94   5.463%   $251.9933   $251.99   $252.00   $252.00  
  Purchase #3 $63.58   8.782%   $69.1636   $69.16   $69.15   $69.20  
  Purchase #4 $179.99   6.831%   $192.2851   $192.29   $192.30   $192.30  
  Purchase #5 $168.47   8.775%   $183.2532   $183.25   $183.25   $183.30  
  Purchase #6 $224.99   3.748%   $233.4226   $233.42   $233.40   $233.40  
  Purchase #7 $192.57   12.712%   $217.0495   $217.05   $217.05   $217.00  
  7 purchase totals = $1,166.13       $1,251.7867   $1,251.78   $1,251.75   $1,251.80