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	$214.70	8.592%	$233.147	$233.15	$233.15	$233.10
Purchase #2	$197.91	13.533%	$224.6932	$224.69	$224.70	$224.70
Purchase #3	$148.92	11.472%	$166.0041	$166.00	$166.00	$166.00
Purchase #4	$159.61	5.563%	$168.4891	$168.49	$168.50	$168.50
Purchase #5	$113.82	11.703%	$127.1404	$127.14	$127.15	$127.10
Purchase #6	$32.56	10.196%	$35.8798	$35.88	$35.90	$35.90
Purchase #7	$28.91	10.160%	$31.8473	$31.85	$31.85	$31.80
7 purchase totals =	$896.43		$987.2009	$987.20	$987.25	$987.10