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	$127.71	4.727%	$133.7469	$133.75	$133.75	$133.70
Purchase #2	$151.86	13.391%	$172.1956	$172.20	$172.20	$172.20
Purchase #3	$200.93	10.576%	$222.1804	$222.18	$222.20	$222.20
Purchase #4	$79.30	13.824%	$90.2624	$90.26	$90.25	$90.30
Purchase #5	$241.43	6.771%	$257.7772	$257.78	$257.80	$257.80
Purchase #6	$80.67	11.159%	$89.672	$89.67	$89.65	$89.70
Purchase #7	$30.77	11.853%	$34.4172	$34.42	$34.40	$34.40
7 purchase totals =	$912.67		$1,000.2517	$1,000.26	$1,000.25	$1,000.30