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	$179.39	5.512%	$189.278	$189.28	$189.30	$189.30
Purchase #2	$167.80	3.407%	$173.5169	$173.52	$173.50	$173.50
Purchase #3	$190.86	9.783%	$209.5318	$209.53	$209.55	$209.50
Purchase #4	$138.56	13.127%	$156.7488	$156.75	$156.75	$156.70
Purchase #5	$209.55	9.467%	$229.3881	$229.39	$229.40	$229.40
Purchase #6	$13.90	12.158%	$15.59	$15.59	$15.60	$15.60
Purchase #7	$95.45	12.544%	$107.4232	$107.42	$107.40	$107.40
7 purchase totals =	$995.51		$1,081.4768	$1,081.48	$1,081.50	$1,081.40