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	$75.82	12.391%	$85.2149	$85.21	$85.20	$85.20
Purchase #2	$20.88	4.491%	$21.8177	$21.82	$21.80	$21.80
Purchase #3	$53.29	7.626%	$57.3539	$57.35	$57.35	$57.40
Purchase #4	$29.81	11.400%	$33.2083	$33.21	$33.20	$33.20
Purchase #5	$160.35	7.285%	$172.0315	$172.03	$172.05	$172.00
Purchase #6	$235.58	10.730%	$260.8577	$260.86	$260.85	$260.90
Purchase #7	$86.83	5.805%	$91.8705	$91.87	$91.85	$91.90
7 purchase totals =	$662.56		$722.3545	$722.35	$722.30	$722.40