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	$162.50	4.475%	$169.7719	$169.77	$169.75	$169.80
Purchase #2	$243.28	11.596%	$271.4907	$271.49	$271.50	$271.50
Purchase #3	$77.48	6.395%	$82.4348	$82.43	$82.45	$82.40
Purchase #4	$235.62	11.456%	$262.6126	$262.61	$262.60	$262.60
Purchase #5	$173.35	7.210%	$185.8485	$185.85	$185.85	$185.80
Purchase #6	$26.98	5.839%	$28.5554	$28.56	$28.55	$28.60
Purchase #7	$46.51	4.741%	$48.715	$48.72	$48.70	$48.70
7 purchase totals =	$965.72		$1,049.4289	$1,049.43	$1,049.40	$1,049.40