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	$76.98	3.528%	$79.6959	$79.70	$79.70	$79.70
Purchase #2	$15.96	10.213%	$17.59	$17.59	$17.60	$17.60
Purchase #3	$84.71	11.426%	$94.389	$94.39	$94.40	$94.40
Purchase #4	$64.42	3.421%	$66.6238	$66.62	$66.60	$66.60
Purchase #5	$10.38	7.385%	$11.1466	$11.15	$11.15	$11.10
Purchase #6	$117.30	5.373%	$123.6025	$123.60	$123.60	$123.60
Purchase #7	$74.50	4.829%	$78.0976	$78.10	$78.10	$78.10
7 purchase totals =	$444.25		$471.1454	$471.15	$471.15	$471.10