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	$151.73	4.594%	$158.7005	$158.70	$158.70	$158.70
Purchase #2	$203.69	5.301%	$214.4876	$214.49	$214.50	$214.50
Purchase #3	$233.60	9.386%	$255.5257	$255.53	$255.55	$255.50
Purchase #4	$150.45	12.714%	$169.5782	$169.58	$169.60	$169.60
Purchase #5	$51.32	5.582%	$54.1847	$54.18	$54.20	$54.20
Purchase #6	$64.27	4.217%	$66.9803	$66.98	$67.00	$67.00
Purchase #7	$45.68	3.748%	$47.3921	$47.39	$47.40	$47.40
7 purchase totals =	$900.74		$966.8491	$966.85	$966.95	$966.90