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	$178.31	8.659%	$193.7499	$193.75	$193.75	$193.70
Purchase #2	$83.74	13.852%	$95.3397	$95.34	$95.35	$95.30
Purchase #3	$73.26	6.863%	$78.2878	$78.29	$78.30	$78.30
Purchase #4	$234.56	3.832%	$243.5483	$243.55	$243.55	$243.50
Purchase #5	$244.45	13.787%	$278.1523	$278.15	$278.15	$278.20
Purchase #6	$194.85	11.344%	$216.9538	$216.95	$216.95	$217.00
Purchase #7	$122.33	4.314%	$127.6073	$127.61	$127.60	$127.60
7 purchase totals =	$1,131.50		$1,233.6391	$1,233.64	$1,233.65	$1,233.60