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	$139.77	8.468%	$151.6057	$151.61	$151.60	$151.60
Purchase #2	$64.68	9.438%	$70.7845	$70.78	$70.80	$70.80
Purchase #3	$174.78	5.553%	$184.4855	$184.49	$184.50	$184.50
Purchase #4	$242.66	12.600%	$273.2352	$273.24	$273.25	$273.20
Purchase #5	$91.92	13.769%	$104.5765	$104.58	$104.60	$104.60
Purchase #6	$57.97	12.348%	$65.1281	$65.13	$65.15	$65.10
Purchase #7	$180.91	5.117%	$190.1672	$190.17	$190.15	$190.20
7 purchase totals =	$952.69		$1,039.9827	$1,040.00	$1,040.05	$1,040.00