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	$132.71	3.632%	$137.53	$137.53	$137.55	$137.50
Purchase #2	$151.28	7.707%	$162.9391	$162.94	$162.95	$162.90
Purchase #3	$89.78	13.160%	$101.595	$101.60	$101.60	$101.60
Purchase #4	$173.59	4.368%	$181.1724	$181.17	$181.15	$181.20
Purchase #5	$191.99	13.570%	$218.043	$218.04	$218.05	$218.00
Purchase #6	$100.27	11.491%	$111.792	$111.79	$111.80	$111.80
Purchase #7	$98.93	6.457%	$105.3179	$105.32	$105.30	$105.30
7 purchase totals =	$938.55		$1,018.3894	$1,018.39	$1,018.40	$1,018.30