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 $86.48   9.438%   $94.642   $94.64   $94.65   $94.60  
  Purchase #2 $163.27   8.551%   $177.2312   $177.23   $177.25   $177.20  
  Purchase #3 $237.98   6.516%   $253.4868   $253.49   $253.50   $253.50  
  Purchase #4 $206.79   13.126%   $233.9333   $233.93   $233.95   $233.90  
  Purchase #5 $221.75   11.862%   $248.054   $248.05   $248.05   $248.10  
  Purchase #6 $65.62   4.489%   $68.5657   $68.57   $68.55   $68.60  
  Purchase #7 $187.89   10.473%   $207.5677   $207.57   $207.55   $207.60  
  7 purchase totals = $1,169.78       $1,283.4807   $1,283.48   $1,283.50   $1,283.50