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	$85.67	10.277%	$94.4743	$94.47	$94.45	$94.50
Purchase #2	$15.66	7.117%	$16.7745	$16.77	$16.75	$16.80
Purchase #3	$85.69	6.128%	$90.9411	$90.94	$90.95	$90.90
Purchase #4	$47.82	4.732%	$50.0828	$50.08	$50.10	$50.10
Purchase #5	$41.83	11.560%	$46.6655	$46.67	$46.65	$46.70
Purchase #6	$33.37	12.141%	$37.4215	$37.42	$37.40	$37.40
Purchase #7	$10.55	3.526%	$10.922	$10.92	$10.90	$10.90
7 purchase totals =	$320.59		$347.2817	$347.27	$347.20	$347.30