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 $105.62   8.829%   $114.9452   $114.95   $114.95   $114.90  
  Purchase #2 $83.75   9.104%   $91.3746   $91.37   $91.35   $91.40  
  Purchase #3 $216.91   12.243%   $243.4663   $243.47   $243.45   $243.50  
  Purchase #4 $119.74   6.246%   $127.219   $127.22   $127.20   $127.20  
  Purchase #5 $173.46   5.375%   $182.7835   $182.78   $182.80   $182.80  
  Purchase #6 $218.72   13.269%   $247.742   $247.74   $247.75   $247.70  
  Purchase #7 $148.94   6.729%   $158.9622   $158.96   $158.95   $159.00  
  7 purchase totals = $1,067.14       $1,166.4928   $1,166.49   $1,166.45   $1,166.50