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	$216.51	13.500%	$245.7389	$245.74	$245.75	$245.70
Purchase #2	$81.33	12.828%	$91.763	$91.76	$91.75	$91.80
Purchase #3	$239.90	12.403%	$269.6548	$269.65	$269.65	$269.70
Purchase #4	$228.83	9.491%	$250.5483	$250.55	$250.55	$250.50
Purchase #5	$181.73	5.734%	$192.1504	$192.15	$192.15	$192.20
Purchase #6	$166.29	4.349%	$173.522	$173.52	$173.50	$173.50
Purchase #7	$90.67	9.273%	$99.0778	$99.08	$99.10	$99.10
7 purchase totals =	$1,205.26		$1,322.4552	$1,322.45	$1,322.45	$1,322.50