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	$54.95	3.461%	$56.8518	$56.85	$56.85	$56.90
Purchase #2	$220.37	12.659%	$248.2666	$248.27	$248.25	$248.30
Purchase #3	$19.73	7.520%	$21.2137	$21.21	$21.20	$21.20
Purchase #4	$122.36	4.443%	$127.7965	$127.80	$127.80	$127.80
Purchase #5	$177.60	7.433%	$190.801	$190.80	$190.80	$190.80
Purchase #6	$59.27	12.463%	$66.6568	$66.66	$66.65	$66.70
Purchase #7	$148.45	13.829%	$168.9792	$168.98	$169.00	$169.00
7 purchase totals =	$802.73		$880.5656	$880.57	$880.55	$880.70