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	$58.32	7.447%	$62.6631	$62.66	$62.65	$62.70
Purchase #2	$235.47	11.767%	$263.1778	$263.18	$263.20	$263.20
Purchase #3	$90.45	11.150%	$100.5352	$100.54	$100.55	$100.50
Purchase #4	$11.75	4.234%	$12.2475	$12.25	$12.25	$12.20
Purchase #5	$45.44	3.644%	$47.0958	$47.10	$47.10	$47.10
Purchase #6	$103.54	7.259%	$111.056	$111.06	$111.05	$111.10
Purchase #7	$152.26	5.208%	$160.1897	$160.19	$160.20	$160.20
7 purchase totals =	$697.23		$756.9651	$756.98	$757.00	$757.00