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	$105.31	8.472%	$114.2319	$114.23	$114.25	$114.20
Purchase #2	$106.62	4.446%	$111.3603	$111.36	$111.35	$111.40
Purchase #3	$94.51	5.784%	$99.9765	$99.98	$100.00	$100.00
Purchase #4	$135.83	13.675%	$154.4048	$154.40	$154.40	$154.40
Purchase #5	$157.62	9.844%	$173.1361	$173.14	$173.15	$173.10
Purchase #6	$51.96	8.631%	$56.4447	$56.44	$56.45	$56.40
Purchase #7	$144.50	13.548%	$164.0769	$164.08	$164.10	$164.10
7 purchase totals =	$796.35		$873.6312	$873.63	$873.70	$873.60