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	$82.38	3.685%	$85.4157	$85.42	$85.40	$85.40
Purchase #2	$180.57	3.544%	$186.9694	$186.97	$186.95	$187.00
Purchase #3	$250.28	5.611%	$264.3232	$264.32	$264.30	$264.30
Purchase #4	$148.86	13.445%	$168.8742	$168.87	$168.85	$168.90
Purchase #5	$221.35	7.788%	$238.5887	$238.59	$238.60	$238.60
Purchase #6	$172.38	4.103%	$179.4528	$179.45	$179.45	$179.50
Purchase #7	$128.37	11.607%	$143.2699	$143.27	$143.25	$143.30
7 purchase totals =	$1,184.19		$1,266.8939	$1,266.89	$1,266.80	$1,267.00