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	$105.92	13.117%	$119.8135	$119.81	$119.80	$119.80
Purchase #2	$156.69	7.826%	$168.9526	$168.95	$168.95	$169.00
Purchase #3	$105.45	4.126%	$109.8009	$109.80	$109.80	$109.80
Purchase #4	$14.31	9.409%	$15.6564	$15.66	$15.65	$15.70
Purchase #5	$67.40	13.808%	$76.7066	$76.71	$76.70	$76.70
Purchase #6	$151.77	13.803%	$172.7188	$172.72	$172.70	$172.70
Purchase #7	$97.87	5.286%	$103.0434	$103.04	$103.05	$103.00
7 purchase totals =	$699.41		$766.6922	$766.69	$766.65	$766.70