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	$98.89	13.184%	$111.9277	$111.93	$111.95	$111.90
Purchase #2	$204.49	9.522%	$223.9615	$223.96	$223.95	$224.00
Purchase #3	$50.83	4.602%	$53.1692	$53.17	$53.15	$53.20
Purchase #4	$68.45	10.181%	$75.4189	$75.42	$75.40	$75.40
Purchase #5	$211.55	8.778%	$230.1199	$230.12	$230.10	$230.10
Purchase #6	$146.86	12.538%	$165.2733	$165.27	$165.25	$165.30
Purchase #7	$67.71	9.121%	$73.8858	$73.89	$73.90	$73.90
7 purchase totals =	$848.78		$933.7563	$933.76	$933.70	$933.80