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	$207.29	10.741%	$229.555	$229.56	$229.55	$229.60
Purchase #2	$17.32	11.400%	$19.2945	$19.29	$19.30	$19.30
Purchase #3	$179.91	11.663%	$200.8929	$200.89	$200.90	$200.90
Purchase #4	$183.84	10.318%	$202.8086	$202.81	$202.80	$202.80
Purchase #5	$103.65	3.399%	$107.1731	$107.17	$107.15	$107.20
Purchase #6	$101.53	10.217%	$111.9033	$111.90	$111.90	$111.90
Purchase #7	$121.92	7.362%	$130.8958	$130.90	$130.90	$130.90
7 purchase totals =	$915.46		$1,002.5232	$1,002.52	$1,002.50	$1,002.60