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	$231.97	5.543%	$244.8281	$244.83	$244.85	$244.80
Purchase #2	$145.84	9.427%	$159.5883	$159.59	$159.60	$159.60
Purchase #3	$89.26	11.426%	$99.4588	$99.46	$99.45	$99.50
Purchase #4	$211.42	4.852%	$221.6781	$221.68	$221.70	$221.70
Purchase #5	$93.61	12.213%	$105.0426	$105.04	$105.05	$105.00
Purchase #6	$78.83	7.624%	$84.84	$84.84	$84.85	$84.80
Purchase #7	$202.61	4.666%	$212.0638	$212.06	$212.05	$212.10
7 purchase totals =	$1,053.54		$1,127.4997	$1,127.50	$1,127.55	$1,127.50