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	$82.83	9.225%	$90.4711	$90.47	$90.45	$90.50
Purchase #2	$17.35	13.812%	$19.7464	$19.75	$19.75	$19.70
Purchase #3	$35.28	5.694%	$37.2888	$37.29	$37.30	$37.30
Purchase #4	$76.42	5.233%	$80.4191	$80.42	$80.40	$80.40
Purchase #5	$184.34	6.109%	$195.6013	$195.60	$195.60	$195.60
Purchase #6	$67.64	4.233%	$70.5032	$70.50	$70.50	$70.50
Purchase #7	$211.29	10.437%	$233.3423	$233.34	$233.35	$233.30
7 purchase totals =	$675.15		$727.3722	$727.37	$727.35	$727.30