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	$143.99	6.246%	$152.9836	$152.98	$153.00	$153.00
Purchase #2	$149.89	11.255%	$166.7601	$166.76	$166.75	$166.80
Purchase #3	$100.45	8.621%	$109.1098	$109.11	$109.10	$109.10
Purchase #4	$143.68	5.440%	$151.4962	$151.50	$151.50	$151.50
Purchase #5	$136.96	10.863%	$151.838	$151.84	$151.85	$151.80
Purchase #6	$77.60	7.323%	$83.2826	$83.28	$83.30	$83.30
Purchase #7	$110.89	4.684%	$116.0841	$116.08	$116.10	$116.10
7 purchase totals =	$863.46		$931.5544	$931.55	$931.60	$931.60