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	$231.34	4.219%	$241.1002	$241.10	$241.10	$241.10
Purchase #2	$152.56	9.202%	$166.5986	$166.60	$166.60	$166.60
Purchase #3	$141.53	8.155%	$153.0718	$153.07	$153.05	$153.10
Purchase #4	$79.43	5.247%	$83.5977	$83.60	$83.60	$83.60
Purchase #5	$134.57	10.636%	$148.8829	$148.88	$148.90	$148.90
Purchase #6	$217.37	5.499%	$229.3232	$229.32	$229.30	$229.30
Purchase #7	$125.64	13.413%	$142.4921	$142.49	$142.50	$142.50
7 purchase totals =	$1,082.44		$1,165.0665	$1,165.06	$1,165.05	$1,165.10