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 $44.39   3.694%   $46.0298   $46.03   $46.05   $46.00  
  Purchase #2 $112.80   3.280%   $116.4998   $116.50   $116.50   $116.50  
  Purchase #3 $248.92   6.600%   $265.3487   $265.35   $265.35   $265.30  
  Purchase #4 $85.48   13.366%   $96.9053   $96.91   $96.90   $96.90  
  Purchase #5 $233.78   6.272%   $248.4427   $248.44   $248.45   $248.40  
  Purchase #6 $99.85   4.177%   $104.0207   $104.02   $104.00   $104.00  
  Purchase #7 $96.77   9.216%   $105.6883   $105.69   $105.70   $105.70  
  7 purchase totals = $921.99       $982.9353   $982.94   $982.95   $982.80