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	$178.72	3.844%	$185.59	$185.59	$185.60	$185.60
Purchase #2	$15.45	12.408%	$17.367	$17.37	$17.35	$17.40
Purchase #3	$50.86	4.588%	$53.1935	$53.19	$53.20	$53.20
Purchase #4	$65.87	13.123%	$74.5141	$74.51	$74.50	$74.50
Purchase #5	$83.54	8.600%	$90.7244	$90.72	$90.70	$90.70
Purchase #6	$147.79	4.451%	$154.3681	$154.37	$154.35	$154.40
Purchase #7	$194.64	7.404%	$209.0511	$209.05	$209.05	$209.10
7 purchase totals =	$736.87		$784.8082	$784.80	$784.75	$784.90