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	$223.72	3.485%	$231.5166	$231.52	$231.50	$231.50
Purchase #2	$234.56	3.305%	$242.3122	$242.31	$242.30	$242.30
Purchase #3	$31.56	4.474%	$32.972	$32.97	$32.95	$33.00
Purchase #4	$19.37	6.668%	$20.6616	$20.66	$20.65	$20.70
Purchase #5	$166.85	6.727%	$178.074	$178.07	$178.05	$178.10
Purchase #6	$37.35	12.793%	$42.1282	$42.13	$42.15	$42.10
Purchase #7	$120.66	4.526%	$126.1211	$126.12	$126.10	$126.10
7 purchase totals =	$834.07		$873.7857	$873.78	$873.70	$873.80