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	$197.49	12.579%	$222.3323	$222.33	$222.35	$222.30
Purchase #2	$30.84	6.113%	$32.7252	$32.73	$32.75	$32.70
Purchase #3	$205.49	12.764%	$231.7187	$231.72	$231.70	$231.70
Purchase #4	$185.50	7.401%	$199.2289	$199.23	$199.25	$199.20
Purchase #5	$40.90	6.251%	$43.4567	$43.46	$43.45	$43.50
Purchase #6	$147.52	4.341%	$153.9238	$153.92	$153.90	$153.90
Purchase #7	$138.83	3.838%	$144.1583	$144.16	$144.15	$144.20
7 purchase totals =	$946.57		$1,027.5439	$1,027.55	$1,027.55	$1,027.50