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 $62.30   10.653%   $68.9368   $68.94   $68.95   $68.90  
  Purchase #2 $230.32   9.664%   $252.5781   $252.58   $252.60   $252.60  
  Purchase #3 $162.42   7.205%   $174.1224   $174.12   $174.10   $174.10  
  Purchase #4 $154.74   10.168%   $170.474   $170.47   $170.45   $170.50  
  Purchase #5 $74.42   11.156%   $82.7223   $82.72   $82.70   $82.70  
  Purchase #6 $196.71   6.190%   $208.8863   $208.89   $208.90   $208.90  
  Purchase #7 $173.28   11.313%   $192.8832   $192.88   $192.90   $192.90  
  7 purchase totals = $1,054.19       $1,150.6031   $1,150.60   $1,150.60   $1,150.60