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 $113.82   10.695%   $125.993   $125.99   $126.00   $126.00  
  Purchase #2 $71.89   10.116%   $79.1624   $79.16   $79.15   $79.20  
  Purchase #3 $159.85   10.272%   $176.2698   $176.27   $176.25   $176.30  
  Purchase #4 $82.70   10.277%   $91.1991   $91.20   $91.20   $91.20  
  Purchase #5 $171.33   3.366%   $177.097   $177.10   $177.10   $177.10  
  Purchase #6 $203.68   10.858%   $225.7956   $225.80   $225.80   $225.80  
  Purchase #7 $185.86   9.113%   $202.7974   $202.80   $202.80   $202.80  
  7 purchase totals = $989.13       $1,078.3143   $1,078.32   $1,078.30   $1,078.40