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	$162.82	11.732%	$181.922	$181.92	$181.90	$181.90
Purchase #2	$141.63	8.514%	$153.6884	$153.69	$153.70	$153.70
Purchase #3	$142.41	7.347%	$152.8729	$152.87	$152.85	$152.90
Purchase #4	$138.88	12.230%	$155.865	$155.87	$155.85	$155.90
Purchase #5	$57.37	4.379%	$59.8822	$59.88	$59.90	$59.90
Purchase #6	$52.30	4.531%	$54.6697	$54.67	$54.65	$54.70
Purchase #7	$109.72	7.702%	$118.1706	$118.17	$118.15	$118.20
7 purchase totals =	$805.13		$877.0708	$877.07	$877.00	$877.20