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	$95.49	9.407%	$104.4727	$104.47	$104.45	$104.50
Purchase #2	$60.58	10.836%	$67.1444	$67.14	$67.15	$67.10
Purchase #3	$218.46	5.298%	$230.034	$230.03	$230.05	$230.00
Purchase #4	$62.35	5.117%	$65.5404	$65.54	$65.55	$65.50
Purchase #5	$52.56	11.730%	$58.7253	$58.73	$58.75	$58.70
Purchase #6	$75.74	3.433%	$78.3402	$78.34	$78.35	$78.30
Purchase #7	$153.78	5.718%	$162.5731	$162.57	$162.55	$162.60
7 purchase totals =	$718.96		$766.8301	$766.82	$766.85	$766.70