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	$160.55	9.294%	$175.4715	$175.47	$175.45	$175.50
Purchase #2	$17.52	9.320%	$19.1529	$19.15	$19.15	$19.20
Purchase #3	$230.42	4.645%	$241.123	$241.12	$241.10	$241.10
Purchase #4	$200.94	8.517%	$218.0541	$218.05	$218.05	$218.10
Purchase #5	$28.25	3.226%	$29.1613	$29.16	$29.15	$29.20
Purchase #6	$75.60	3.303%	$78.0971	$78.10	$78.10	$78.10
Purchase #7	$171.91	7.801%	$185.3207	$185.32	$185.30	$185.30
7 purchase totals =	$885.19		$946.3806	$946.37	$946.30	$946.50