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	$206.43	4.493%	$215.7049	$215.70	$215.70	$215.70
Purchase #2	$219.52	4.774%	$229.9999	$230.00	$230.00	$230.00
Purchase #3	$240.33	13.725%	$273.3153	$273.32	$273.30	$273.30
Purchase #4	$196.43	9.577%	$215.2421	$215.24	$215.25	$215.20
Purchase #5	$194.27	5.181%	$204.3351	$204.34	$204.35	$204.30
Purchase #6	$158.83	4.176%	$165.4627	$165.46	$165.45	$165.50
Purchase #7	$157.69	9.440%	$172.5759	$172.58	$172.60	$172.60
7 purchase totals =	$1,373.50		$1,476.6359	$1,476.64	$1,476.65	$1,476.60