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	$207.74	5.810%	$219.8097	$219.81	$219.80	$219.80
Purchase #2	$114.57	5.643%	$121.0352	$121.04	$121.05	$121.00
Purchase #3	$85.95	6.204%	$91.2823	$91.28	$91.30	$91.30
Purchase #4	$157.67	9.358%	$172.4248	$172.42	$172.40	$172.40
Purchase #5	$148.90	11.653%	$166.2513	$166.25	$166.25	$166.30
Purchase #6	$50.58	8.446%	$54.852	$54.85	$54.85	$54.90
Purchase #7	$109.59	6.286%	$116.4788	$116.48	$116.50	$116.50
7 purchase totals =	$875.00		$942.1341	$942.13	$942.15	$942.20