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	$122.62	3.626%	$127.0662	$127.07	$127.05	$127.10
Purchase #2	$118.67	4.278%	$123.7467	$123.75	$123.75	$123.70
Purchase #3	$77.52	10.775%	$85.8728	$85.87	$85.85	$85.90
Purchase #4	$171.80	8.611%	$186.5937	$186.59	$186.60	$186.60
Purchase #5	$53.64	6.698%	$57.2328	$57.23	$57.25	$57.20
Purchase #6	$181.80	3.143%	$187.514	$187.51	$187.50	$187.50
Purchase #7	$60.80	8.793%	$66.1461	$66.15	$66.15	$66.10
7 purchase totals =	$786.85		$834.1723	$834.17	$834.15	$834.10