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	$105.27	5.473%	$111.0314	$111.03	$111.05	$111.00
Purchase #2	$204.48	10.811%	$226.5863	$226.59	$226.60	$226.60
Purchase #3	$71.31	13.838%	$81.1779	$81.18	$81.20	$81.20
Purchase #4	$138.85	7.609%	$149.4151	$149.42	$149.40	$149.40
Purchase #5	$91.77	4.753%	$96.1318	$96.13	$96.15	$96.10
Purchase #6	$137.79	9.874%	$151.3954	$151.40	$151.40	$151.40
Purchase #7	$145.62	4.729%	$152.5064	$152.51	$152.50	$152.50
7 purchase totals =	$895.09		$968.2443	$968.26	$968.30	$968.20