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	$235.79	7.752%	$254.0684	$254.07	$254.05	$254.10
Purchase #2	$89.66	10.856%	$99.3935	$99.39	$99.40	$99.40
Purchase #3	$201.95	10.485%	$223.1245	$223.12	$223.10	$223.10
Purchase #4	$111.83	13.458%	$126.8801	$126.88	$126.90	$126.90
Purchase #5	$216.64	6.304%	$230.297	$230.30	$230.30	$230.30
Purchase #6	$167.52	12.427%	$188.3377	$188.34	$188.35	$188.30
Purchase #7	$70.76	5.336%	$74.5358	$74.54	$74.55	$74.50
7 purchase totals =	$1,094.15		$1,196.6370	$1,196.64	$1,196.65	$1,196.60