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	$165.52	11.602%	$184.7236	$184.72	$184.70	$184.70
Purchase #2	$9.83	7.694%	$10.5863	$10.59	$10.60	$10.60
Purchase #3	$24.37	3.126%	$25.1318	$25.13	$25.15	$25.10
Purchase #4	$9.30	8.382%	$10.0795	$10.08	$10.10	$10.10
Purchase #5	$62.80	7.459%	$67.4843	$67.48	$67.50	$67.50
Purchase #6	$97.57	7.394%	$104.7843	$104.78	$104.80	$104.80
Purchase #7	$91.68	5.160%	$96.4107	$96.41	$96.40	$96.40
7 purchase totals =	$461.07		$499.2005	$499.19	$499.25	$499.20