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	$172.44	7.800%	$185.8903	$185.89	$185.90	$185.90
Purchase #2	$79.39	6.779%	$84.7718	$84.77	$84.75	$84.80
Purchase #3	$49.97	9.264%	$54.5992	$54.60	$54.60	$54.60
Purchase #4	$90.93	5.299%	$95.7484	$95.75	$95.75	$95.70
Purchase #5	$32.45	5.869%	$34.3545	$34.35	$34.35	$34.40
Purchase #6	$70.71	10.149%	$77.8864	$77.89	$77.90	$77.90
Purchase #7	$51.84	4.708%	$54.2806	$54.28	$54.30	$54.30
7 purchase totals =	$547.73		$587.5312	$587.53	$587.55	$587.60