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	$49.54	4.188%	$51.6147	$51.61	$51.60	$51.60
Purchase #2	$146.66	8.564%	$159.22	$159.22	$159.20	$159.20
Purchase #3	$40.66	5.510%	$42.9004	$42.90	$42.90	$42.90
Purchase #4	$9.46	4.835%	$9.9174	$9.92	$9.90	$9.90
Purchase #5	$19.39	6.422%	$20.6352	$20.64	$20.65	$20.60
Purchase #6	$83.28	11.196%	$92.604	$92.60	$92.60	$92.60
Purchase #7	$163.40	13.241%	$185.0358	$185.04	$185.05	$185.00
7 purchase totals =	$512.39		$561.9275	$561.93	$561.90	$561.80