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	$131.87	10.590%	$145.835	$145.84	$145.85	$145.80
Purchase #2	$196.43	9.211%	$214.5232	$214.52	$214.50	$214.50
Purchase #3	$55.59	6.424%	$59.1611	$59.16	$59.15	$59.20
Purchase #4	$156.68	11.308%	$174.3974	$174.40	$174.40	$174.40
Purchase #5	$244.51	12.601%	$275.3207	$275.32	$275.30	$275.30
Purchase #6	$179.78	5.503%	$189.6733	$189.67	$189.65	$189.70
Purchase #7	$151.56	6.830%	$161.9115	$161.91	$161.90	$161.90
7 purchase totals =	$1,116.42		$1,220.8222	$1,220.82	$1,220.75	$1,220.80