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 $228.50   5.772%   $241.689   $241.69   $241.70   $241.70  
  Purchase #2 $234.87   5.644%   $248.1261   $248.13   $248.15   $248.10  
  Purchase #3 $58.43   12.397%   $65.6736   $65.67   $65.65   $65.70  
  Purchase #4 $63.99   8.604%   $69.4957   $69.50   $69.50   $69.50  
  Purchase #5 $164.67   10.619%   $182.1563   $182.16   $182.15   $182.20  
  Purchase #6 $101.42   5.354%   $106.85   $106.85   $106.85   $106.90  
  Purchase #7 $100.77   4.182%   $104.9842   $104.98   $105.00   $105.00  
  7 purchase totals = $952.65       $1,018.9749   $1,018.98   $1,019.00   $1,019.10