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 $248.47   8.297%   $269.0856   $269.09   $269.10   $269.10  
  Purchase #2 $58.82   3.441%   $60.844   $60.84   $60.85   $60.80  
  Purchase #3 $193.47   11.791%   $216.282   $216.28   $216.30   $216.30  
  Purchase #4 $118.26   6.659%   $126.1349   $126.13   $126.15   $126.10  
  Purchase #5 $58.48   6.594%   $62.3362   $62.34   $62.35   $62.30  
  Purchase #6 $79.87   8.771%   $86.8754   $86.88   $86.90   $86.90  
  Purchase #7 $237.31   4.114%   $247.0729   $247.07   $247.05   $247.10  
  7 purchase totals = $994.68       $1,068.6310   $1,068.63   $1,068.70   $1,068.60