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	$40.92	11.183%	$45.4961	$45.50	$45.50	$45.50
Purchase #2	$234.41	5.624%	$247.5932	$247.59	$247.60	$247.60
Purchase #3	$94.76	4.641%	$99.1578	$99.16	$99.15	$99.20
Purchase #4	$155.83	7.361%	$167.3006	$167.30	$167.30	$167.30
Purchase #5	$164.28	8.454%	$178.1682	$178.17	$178.15	$178.20
Purchase #6	$228.83	5.707%	$241.8893	$241.89	$241.90	$241.90
Purchase #7	$96.54	8.805%	$105.0403	$105.04	$105.05	$105.00
7 purchase totals =	$1,015.57		$1,084.6455	$1,084.65	$1,084.65	$1,084.70