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	$39.95	10.255%	$44.0469	$44.05	$44.05	$44.00
Purchase #2	$57.43	3.839%	$59.6347	$59.63	$59.65	$59.60
Purchase #3	$58.74	11.362%	$65.414	$65.41	$65.40	$65.40
Purchase #4	$128.29	13.683%	$145.8439	$145.84	$145.85	$145.80
Purchase #5	$207.62	7.773%	$223.7583	$223.76	$223.75	$223.80
Purchase #6	$125.80	13.779%	$143.134	$143.13	$143.15	$143.10
Purchase #7	$81.36	11.565%	$90.7693	$90.77	$90.75	$90.80
7 purchase totals =	$699.19		$772.6011	$772.59	$772.60	$772.50