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	$225.39	5.737%	$238.3206	$238.32	$238.30	$238.30
Purchase #2	$53.83	4.265%	$56.1258	$56.13	$56.15	$56.10
Purchase #3	$16.31	13.416%	$18.4981	$18.50	$18.50	$18.50
Purchase #4	$83.77	13.469%	$95.053	$95.05	$95.05	$95.10
Purchase #5	$141.59	4.631%	$148.147	$148.15	$148.15	$148.10
Purchase #6	$132.30	10.824%	$146.6202	$146.62	$146.60	$146.60
Purchase #7	$118.90	11.701%	$132.8125	$132.81	$132.80	$132.80
7 purchase totals =	$772.09		$835.5772	$835.58	$835.55	$835.50