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	$217.75	11.364%	$242.4951	$242.50	$242.50	$242.50
Purchase #2	$137.50	4.431%	$143.5926	$143.59	$143.60	$143.60
Purchase #3	$146.54	3.449%	$151.5942	$151.59	$151.60	$151.60
Purchase #4	$85.38	8.633%	$92.7509	$92.75	$92.75	$92.80
Purchase #5	$202.72	8.747%	$220.4519	$220.45	$220.45	$220.50
Purchase #6	$198.31	13.488%	$225.0581	$225.06	$225.05	$225.10
Purchase #7	$68.27	12.493%	$76.799	$76.80	$76.80	$76.80
7 purchase totals =	$1,056.47		$1,152.7418	$1,152.74	$1,152.75	$1,152.90