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	$111.88	3.698%	$116.0173	$116.02	$116.00	$116.00
Purchase #2	$30.29	13.124%	$34.2653	$34.27	$34.25	$34.30
Purchase #3	$229.43	6.533%	$244.4187	$244.42	$244.40	$244.40
Purchase #4	$120.47	5.530%	$127.132	$127.13	$127.15	$127.10
Purchase #5	$108.78	3.106%	$112.1587	$112.16	$112.15	$112.20
Purchase #6	$101.71	11.747%	$113.6579	$113.66	$113.65	$113.70
Purchase #7	$31.79	3.840%	$33.0107	$33.01	$33.00	$33.00
7 purchase totals =	$734.35		$780.6606	$780.67	$780.60	$780.70