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 $46.95   5.606%   $49.582   $49.58   $49.60   $49.60  
  Purchase #2 $215.77   11.747%   $241.1165   $241.12   $241.10   $241.10  
  Purchase #3 $122.39   10.871%   $135.695   $135.70   $135.70   $135.70  
  Purchase #4 $118.84   13.104%   $134.4128   $134.41   $134.40   $134.40  
  Purchase #5 $84.63   5.853%   $89.5834   $89.58   $89.60   $89.60  
  Purchase #6 $168.60   10.435%   $186.1934   $186.19   $186.20   $186.20  
  Purchase #7 $243.32   10.126%   $267.9586   $267.96   $267.95   $268.00  
  7 purchase totals = $1,000.50       $1,104.5417   $1,104.54   $1,104.55   $1,104.60