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	$57.88	5.762%	$61.215	$61.22	$61.20	$61.20
Purchase #2	$42.64	5.602%	$45.0287	$45.03	$45.05	$45.00
Purchase #3	$93.70	7.707%	$100.9215	$100.92	$100.90	$100.90
Purchase #4	$63.81	9.753%	$70.0334	$70.03	$70.05	$70.00
Purchase #5	$42.85	12.201%	$48.0781	$48.08	$48.10	$48.10
Purchase #6	$172.29	6.130%	$182.8514	$182.85	$182.85	$182.90
Purchase #7	$96.76	12.158%	$108.5241	$108.52	$108.50	$108.50
7 purchase totals =	$569.93		$616.6522	$616.65	$616.65	$616.60