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	$109.93	6.233%	$116.7819	$116.78	$116.80	$116.80
Purchase #2	$79.73	13.779%	$90.716	$90.72	$90.70	$90.70
Purchase #3	$88.27	4.514%	$92.2545	$92.25	$92.25	$92.30
Purchase #4	$241.76	9.163%	$263.9125	$263.91	$263.90	$263.90
Purchase #5	$82.28	6.704%	$87.7961	$87.80	$87.80	$87.80
Purchase #6	$98.79	12.643%	$111.28	$111.28	$111.30	$111.30
Purchase #7	$22.60	5.722%	$23.8932	$23.89	$23.90	$23.90
7 purchase totals =	$723.36		$786.6342	$786.63	$786.65	$786.70