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	$89.76	7.671%	$96.6455	$96.65	$96.65	$96.60
Purchase #2	$173.81	13.187%	$196.7303	$196.73	$196.75	$196.70
Purchase #3	$10.45	11.104%	$11.6104	$11.61	$11.60	$11.60
Purchase #4	$103.83	7.142%	$111.2455	$111.25	$111.25	$111.20
Purchase #5	$193.52	7.443%	$207.9237	$207.92	$207.90	$207.90
Purchase #6	$211.57	5.578%	$223.3714	$223.37	$223.35	$223.40
Purchase #7	$26.92	10.350%	$29.7062	$29.71	$29.70	$29.70
7 purchase totals =	$809.86		$877.2330	$877.24	$877.20	$877.10