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	$59.50	9.633%	$65.2316	$65.23	$65.25	$65.20
Purchase #2	$33.48	11.308%	$37.2659	$37.27	$37.25	$37.30
Purchase #3	$249.54	8.867%	$271.6667	$271.67	$271.65	$271.70
Purchase #4	$241.31	5.326%	$254.1622	$254.16	$254.15	$254.20
Purchase #5	$228.56	8.191%	$247.2813	$247.28	$247.30	$247.30
Purchase #6	$41.53	11.595%	$46.3454	$46.35	$46.35	$46.30
Purchase #7	$66.86	11.111%	$74.2888	$74.29	$74.30	$74.30
7 purchase totals =	$920.78		$996.2419	$996.25	$996.25	$996.30