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	$144.81	9.484%	$158.5438	$158.54	$158.55	$158.50
Purchase #2	$54.35	5.175%	$57.1626	$57.16	$57.15	$57.20
Purchase #3	$157.31	5.826%	$166.4749	$166.47	$166.45	$166.50
Purchase #4	$131.73	12.569%	$148.2871	$148.29	$148.30	$148.30
Purchase #5	$112.94	3.839%	$117.2758	$117.28	$117.30	$117.30
Purchase #6	$167.91	8.857%	$182.7818	$182.78	$182.80	$182.80
Purchase #7	$209.67	4.248%	$218.5768	$218.58	$218.60	$218.60
7 purchase totals =	$978.72		$1,049.1028	$1,049.10	$1,049.15	$1,049.20