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 $183.91   5.571%   $194.1556   $194.16   $194.15   $194.20  
  Purchase #2 $220.29   10.634%   $243.7156   $243.72   $243.70   $243.70  
  Purchase #3 $29.48   8.253%   $31.913   $31.91   $31.90   $31.90  
  Purchase #4 $172.30   11.660%   $192.3902   $192.39   $192.40   $192.40  
  Purchase #5 $134.49   13.213%   $152.2602   $152.26   $152.25   $152.30  
  Purchase #6 $248.26   9.775%   $272.5274   $272.53   $272.55   $272.50  
  Purchase #7 $84.68   5.487%   $89.3264   $89.33   $89.35   $89.30  
  7 purchase totals = $1,073.41       $1,176.2884   $1,176.30   $1,176.30   $1,176.30