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	$40.30	13.493%	$45.7377	$45.74	$45.75	$45.70
Purchase #2	$16.58	3.530%	$17.1653	$17.17	$17.15	$17.20
Purchase #3	$65.90	9.357%	$72.0663	$72.07	$72.05	$72.10
Purchase #4	$83.65	9.786%	$91.836	$91.84	$91.85	$91.80
Purchase #5	$62.92	13.152%	$71.1952	$71.20	$71.20	$71.20
Purchase #6	$224.89	6.727%	$240.0184	$240.02	$240.00	$240.00
Purchase #7	$123.92	5.831%	$131.1458	$131.15	$131.15	$131.10
7 purchase totals =	$618.16		$669.1647	$669.19	$669.15	$669.10