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	$156.39	12.635%	$176.1499	$176.15	$176.15	$176.10
Purchase #2	$150.40	5.106%	$158.0794	$158.08	$158.10	$158.10
Purchase #3	$145.85	11.598%	$162.7657	$162.77	$162.75	$162.80
Purchase #4	$235.55	10.120%	$259.3877	$259.39	$259.40	$259.40
Purchase #5	$136.45	10.678%	$151.0201	$151.02	$151.00	$151.00
Purchase #6	$60.89	4.450%	$63.5996	$63.60	$63.60	$63.60
Purchase #7	$170.95	5.564%	$180.4617	$180.46	$180.45	$180.50
7 purchase totals =	$1,056.48		$1,151.4641	$1,151.47	$1,151.45	$1,151.50