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 $46.82   5.800%   $49.5356   $49.54   $49.55   $49.50  
  Purchase #2 $207.26   9.712%   $227.3891   $227.39   $227.40   $227.40  
  Purchase #3 $95.64   8.641%   $103.9043   $103.90   $103.90   $103.90  
  Purchase #4 $241.25   5.364%   $254.1907   $254.19   $254.20   $254.20  
  Purchase #5 $228.42   3.450%   $236.3005   $236.30   $236.30   $236.30  
  Purchase #6 $162.87   11.221%   $181.1456   $181.15   $181.15   $181.10  
  Purchase #7 $63.61   4.637%   $66.5596   $66.56   $66.55   $66.60  
  7 purchase totals = $1,045.87       $1,119.0254   $1,119.03   $1,119.05   $1,119.00