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	$154.84	3.530%	$160.3059	$160.31	$160.30	$160.30
Purchase #2	$83.35	7.586%	$89.6729	$89.67	$89.65	$89.70
Purchase #3	$55.93	7.635%	$60.2003	$60.20	$60.20	$60.20
Purchase #4	$48.38	12.304%	$54.3327	$54.33	$54.35	$54.30
Purchase #5	$29.95	4.747%	$31.3717	$31.37	$31.35	$31.40
Purchase #6	$239.67	6.139%	$254.3833	$254.38	$254.40	$254.40
Purchase #7	$143.97	6.717%	$153.6405	$153.64	$153.65	$153.60
7 purchase totals =	$756.09		$803.9073	$803.90	$803.90	$803.90