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	$11.91	3.165%	$12.287	$12.29	$12.30	$12.30
Purchase #2	$56.68	8.316%	$61.3935	$61.39	$61.40	$61.40
Purchase #3	$55.77	11.139%	$61.9822	$61.98	$62.00	$62.00
Purchase #4	$173.92	10.407%	$192.0199	$192.02	$192.00	$192.00
Purchase #5	$95.28	4.537%	$99.6029	$99.60	$99.60	$99.60
Purchase #6	$31.42	11.685%	$35.0914	$35.09	$35.10	$35.10
Purchase #7	$110.35	12.793%	$124.4671	$124.47	$124.45	$124.50
7 purchase totals =	$535.33		$586.8440	$586.84	$586.85	$586.90