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	$134.92	13.763%	$153.489	$153.49	$153.50	$153.50
Purchase #2	$157.35	9.291%	$171.9694	$171.97	$171.95	$172.00
Purchase #3	$152.68	7.816%	$164.6135	$164.61	$164.60	$164.60
Purchase #4	$150.72	5.164%	$158.5032	$158.50	$158.50	$158.50
Purchase #5	$100.38	10.197%	$110.6157	$110.62	$110.60	$110.60
Purchase #6	$72.47	7.782%	$78.1096	$78.11	$78.10	$78.10
Purchase #7	$30.49	9.509%	$33.3893	$33.39	$33.40	$33.40
7 purchase totals =	$799.01		$870.6897	$870.69	$870.65	$870.70