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 $59.53   3.487%   $61.6058   $61.61   $61.60   $61.60  
  Purchase #2 $100.60   3.713%   $104.3353   $104.34   $104.35   $104.30  
  Purchase #3 $60.28   4.813%   $63.1813   $63.18   $63.20   $63.20  
  Purchase #4 $156.25   3.319%   $161.4359   $161.44   $161.45   $161.40  
  Purchase #5 $213.51   10.521%   $235.9734   $235.97   $235.95   $236.00  
  Purchase #6 $106.65   7.235%   $114.3661   $114.37   $114.35   $114.40  
  Purchase #7 $143.99   12.847%   $162.4884   $162.49   $162.50   $162.50  
  7 purchase totals = $840.81       $903.3862   $903.40   $903.40   $903.40