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	$225.31	11.197%	$250.538	$250.54	$250.55	$250.50
Purchase #2	$244.33	4.578%	$255.5154	$255.52	$255.50	$255.50
Purchase #3	$64.79	9.789%	$71.1323	$71.13	$71.15	$71.10
Purchase #4	$99.39	8.662%	$107.9992	$108.00	$108.00	$108.00
Purchase #5	$235.78	6.699%	$251.5749	$251.57	$251.55	$251.60
Purchase #6	$48.30	8.246%	$52.2828	$52.28	$52.30	$52.30
Purchase #7	$88.50	12.558%	$99.6138	$99.61	$99.60	$99.60
7 purchase totals =	$1,006.40		$1,088.6564	$1,088.65	$1,088.65	$1,088.60