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	$211.58	8.699%	$229.9853	$229.99	$230.00	$230.00
Purchase #2	$222.76	6.266%	$236.7181	$236.72	$236.70	$236.70
Purchase #3	$165.99	11.778%	$185.5403	$185.54	$185.55	$185.50
Purchase #4	$177.40	4.388%	$185.1843	$185.18	$185.20	$185.20
Purchase #5	$157.45	11.405%	$175.4072	$175.41	$175.40	$175.40
Purchase #6	$156.79	5.570%	$165.5232	$165.52	$165.50	$165.50
Purchase #7	$204.56	10.392%	$225.8179	$225.82	$225.80	$225.80
7 purchase totals =	$1,296.53		$1,404.1763	$1,404.18	$1,404.15	$1,404.10