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	$241.79	5.139%	$254.2156	$254.22	$254.20	$254.20
Purchase #2	$217.82	5.654%	$230.1355	$230.14	$230.15	$230.10
Purchase #3	$66.65	9.255%	$72.8185	$72.82	$72.80	$72.80
Purchase #4	$217.73	11.690%	$243.1826	$243.18	$243.20	$243.20
Purchase #5	$45.85	10.191%	$50.5226	$50.52	$50.50	$50.50
Purchase #6	$109.76	5.716%	$116.0339	$116.03	$116.05	$116.00
Purchase #7	$181.94	5.160%	$191.3281	$191.33	$191.35	$191.30
7 purchase totals =	$1,081.54		$1,158.2368	$1,158.24	$1,158.25	$1,158.10