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	$29.41	4.485%	$30.729	$30.73	$30.75	$30.70
Purchase #2	$90.71	10.429%	$100.1701	$100.17	$100.15	$100.20
Purchase #3	$176.72	9.389%	$193.3122	$193.31	$193.30	$193.30
Purchase #4	$59.80	7.157%	$64.0799	$64.08	$64.10	$64.10
Purchase #5	$98.44	9.228%	$107.524	$107.52	$107.50	$107.50
Purchase #6	$178.28	4.566%	$186.4203	$186.42	$186.40	$186.40
Purchase #7	$100.82	10.171%	$111.0744	$111.07	$111.05	$111.10
7 purchase totals =	$734.18		$793.3099	$793.30	$793.25	$793.30