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	$43.61	12.497%	$49.0599	$49.06	$49.05	$49.10
Purchase #2	$83.78	5.171%	$88.1123	$88.11	$88.10	$88.10
Purchase #3	$82.90	10.537%	$91.6352	$91.64	$91.65	$91.60
Purchase #4	$238.83	6.530%	$254.4256	$254.43	$254.45	$254.40
Purchase #5	$97.85	7.829%	$105.5107	$105.51	$105.50	$105.50
Purchase #6	$15.99	13.353%	$18.1251	$18.13	$18.15	$18.10
Purchase #7	$94.32	11.443%	$105.113	$105.11	$105.10	$105.10
7 purchase totals =	$657.28		$711.9818	$711.99	$712.00	$711.90