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	$223.51	4.651%	$233.9055	$233.91	$233.90	$233.90
Purchase #2	$85.53	5.482%	$90.2188	$90.22	$90.20	$90.20
Purchase #3	$241.32	7.126%	$258.5165	$258.52	$258.50	$258.50
Purchase #4	$6.67	8.806%	$7.2574	$7.26	$7.25	$7.30
Purchase #5	$106.29	4.497%	$111.0699	$111.07	$111.05	$111.10
Purchase #6	$173.49	9.170%	$189.399	$189.40	$189.40	$189.40
Purchase #7	$60.75	3.588%	$62.9297	$62.93	$62.95	$62.90
7 purchase totals =	$897.56		$953.2968	$953.31	$953.25	$953.30