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	$91.52	9.465%	$100.1824	$100.18	$100.20	$100.20
Purchase #2	$233.83	8.685%	$254.1381	$254.14	$254.15	$254.10
Purchase #3	$66.83	7.819%	$72.0554	$72.06	$72.05	$72.10
Purchase #4	$125.70	3.489%	$130.0857	$130.09	$130.10	$130.10
Purchase #5	$233.32	4.678%	$244.2347	$244.23	$244.25	$244.20
Purchase #6	$68.49	6.374%	$72.8556	$72.86	$72.85	$72.90
Purchase #7	$236.36	8.553%	$256.5759	$256.58	$256.60	$256.60
7 purchase totals =	$1,056.05		$1,130.1278	$1,130.14	$1,130.20	$1,130.20