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	$126.88	4.727%	$132.8776	$132.88	$132.90	$132.90
Purchase #2	$144.92	8.179%	$156.773	$156.77	$156.75	$156.80
Purchase #3	$159.27	10.702%	$176.3151	$176.32	$176.30	$176.30
Purchase #4	$223.28	5.263%	$235.0312	$235.03	$235.05	$235.00
Purchase #5	$161.74	12.243%	$181.5418	$181.54	$181.55	$181.50
Purchase #6	$78.50	13.532%	$89.1226	$89.12	$89.10	$89.10
Purchase #7	$173.65	8.137%	$187.7799	$187.78	$187.80	$187.80
7 purchase totals =	$1,068.24		$1,159.4412	$1,159.44	$1,159.45	$1,159.40