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	$167.40	7.852%	$180.5442	$180.54	$180.55	$180.50
Purchase #2	$34.85	13.298%	$39.4844	$39.48	$39.50	$39.50
Purchase #3	$157.70	10.155%	$173.7144	$173.71	$173.70	$173.70
Purchase #4	$122.88	3.864%	$127.6281	$127.63	$127.65	$127.60
Purchase #5	$166.46	3.147%	$171.6985	$171.70	$171.70	$171.70
Purchase #6	$45.53	11.488%	$50.7605	$50.76	$50.75	$50.80
Purchase #7	$27.53	13.330%	$31.1997	$31.20	$31.20	$31.20
7 purchase totals =	$722.35		$775.0298	$775.02	$775.05	$775.00