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	$141.96	4.266%	$148.016	$148.02	$148.00	$148.00
Purchase #2	$107.93	9.315%	$117.9837	$117.98	$118.00	$118.00
Purchase #3	$128.87	13.714%	$146.5432	$146.54	$146.55	$146.50
Purchase #4	$214.35	9.273%	$234.2267	$234.23	$234.25	$234.20
Purchase #5	$173.66	5.727%	$183.6055	$183.61	$183.60	$183.60
Purchase #6	$148.51	6.602%	$158.3146	$158.31	$158.30	$158.30
Purchase #7	$178.55	6.844%	$190.77	$190.77	$190.75	$190.80
7 purchase totals =	$1,093.83		$1,179.4597	$1,179.46	$1,179.45	$1,179.40