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	$137.27	10.122%	$151.1645	$151.16	$151.15	$151.20
Purchase #2	$142.62	9.205%	$155.7482	$155.75	$155.75	$155.70
Purchase #3	$197.43	5.211%	$207.7181	$207.72	$207.70	$207.70
Purchase #4	$158.81	4.225%	$165.5197	$165.52	$165.50	$165.50
Purchase #5	$59.33	13.680%	$67.4463	$67.45	$67.45	$67.40
Purchase #6	$176.92	8.769%	$192.4341	$192.43	$192.45	$192.40
Purchase #7	$240.78	10.430%	$265.8934	$265.89	$265.90	$265.90
7 purchase totals =	$1,113.16		$1,205.9243	$1,205.92	$1,205.90	$1,205.80