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	$98.58	7.391%	$105.866	$105.87	$105.85	$105.90
Purchase #2	$20.84	3.285%	$21.5246	$21.52	$21.50	$21.50
Purchase #3	$44.55	13.740%	$50.6712	$50.67	$50.65	$50.70
Purchase #4	$243.29	6.385%	$258.8241	$258.82	$258.80	$258.80
Purchase #5	$37.57	8.627%	$40.8112	$40.81	$40.80	$40.80
Purchase #6	$61.97	7.669%	$66.7225	$66.72	$66.70	$66.70
Purchase #7	$13.84	12.708%	$15.5988	$15.60	$15.60	$15.60
7 purchase totals =	$520.64		$560.0184	$560.01	$559.90	$560.00