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	$80.84	5.723%	$85.4665	$85.47	$85.45	$85.50
Purchase #2	$20.94	4.404%	$21.8622	$21.86	$21.85	$21.90
Purchase #3	$81.95	10.188%	$90.2991	$90.30	$90.30	$90.30
Purchase #4	$163.46	5.323%	$172.161	$172.16	$172.15	$172.20
Purchase #5	$67.38	4.444%	$70.3744	$70.37	$70.35	$70.40
Purchase #6	$30.29	5.608%	$31.9887	$31.99	$32.00	$32.00
Purchase #7	$191.38	8.392%	$207.4406	$207.44	$207.45	$207.40
7 purchase totals =	$636.24		$679.5925	$679.59	$679.55	$679.70