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	$147.31	6.461%	$156.8277	$156.83	$156.85	$156.80
Purchase #2	$166.78	3.562%	$172.7207	$172.72	$172.70	$172.70
Purchase #3	$216.26	10.194%	$238.3055	$238.31	$238.30	$238.30
Purchase #4	$40.29	3.810%	$41.825	$41.83	$41.85	$41.80
Purchase #5	$38.47	7.537%	$41.3695	$41.37	$41.35	$41.40
Purchase #6	$36.45	7.501%	$39.1841	$39.18	$39.20	$39.20
Purchase #7	$76.43	7.655%	$82.2807	$82.28	$82.30	$82.30
7 purchase totals =	$721.99		$772.5132	$772.52	$772.55	$772.50