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	$155.66	7.385%	$167.1555	$167.16	$167.15	$167.20
Purchase #2	$78.46	4.338%	$81.8636	$81.86	$81.85	$81.90
Purchase #3	$113.30	12.675%	$127.6608	$127.66	$127.65	$127.70
Purchase #4	$154.91	6.542%	$165.0442	$165.04	$165.05	$165.00
Purchase #5	$64.76	11.608%	$72.2773	$72.28	$72.30	$72.30
Purchase #6	$201.80	11.336%	$224.676	$224.68	$224.70	$224.70
Purchase #7	$51.52	3.870%	$53.5138	$53.51	$53.50	$53.50
7 purchase totals =	$820.41		$892.1912	$892.19	$892.20	$892.30