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	$70.45	4.458%	$73.5907	$73.59	$73.60	$73.60
Purchase #2	$177.89	4.456%	$185.8168	$185.82	$185.80	$185.80
Purchase #3	$141.64	3.505%	$146.6045	$146.60	$146.60	$146.60
Purchase #4	$71.62	10.113%	$78.8629	$78.86	$78.85	$78.90
Purchase #5	$189.47	10.570%	$209.497	$209.50	$209.50	$209.50
Purchase #6	$82.31	13.162%	$93.1436	$93.14	$93.15	$93.10
Purchase #7	$100.45	3.393%	$103.8583	$103.86	$103.85	$103.90
7 purchase totals =	$833.83		$891.3738	$891.37	$891.35	$891.40