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	$198.44	12.592%	$223.4276	$223.43	$223.45	$223.40
Purchase #2	$204.54	12.660%	$230.4348	$230.43	$230.45	$230.40
Purchase #3	$66.59	8.355%	$72.1536	$72.15	$72.15	$72.20
Purchase #4	$241.73	4.113%	$251.6724	$251.67	$251.65	$251.70
Purchase #5	$6.48	8.439%	$7.0268	$7.03	$7.05	$7.00
Purchase #6	$188.51	4.780%	$197.5208	$197.52	$197.50	$197.50
Purchase #7	$172.35	7.527%	$185.3228	$185.32	$185.30	$185.30
7 purchase totals =	$1,078.64		$1,167.5588	$1,167.55	$1,167.55	$1,167.50