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	$62.83	12.785%	$70.8628	$70.86	$70.85	$70.90
Purchase #2	$156.91	10.522%	$173.4201	$173.42	$173.40	$173.40
Purchase #3	$57.53	13.771%	$65.4525	$65.45	$65.45	$65.50
Purchase #4	$210.77	9.294%	$230.359	$230.36	$230.35	$230.40
Purchase #5	$185.49	10.104%	$204.2319	$204.23	$204.25	$204.20
Purchase #6	$103.30	6.110%	$109.6116	$109.61	$109.60	$109.60
Purchase #7	$103.93	5.778%	$109.9351	$109.94	$109.95	$109.90
7 purchase totals =	$880.76		$963.8730	$963.87	$963.85	$963.90