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	$165.57	4.191%	$172.509	$172.51	$172.50	$172.50
Purchase #2	$226.58	5.305%	$238.6001	$238.60	$238.60	$238.60
Purchase #3	$228.53	7.240%	$245.0756	$245.08	$245.10	$245.10
Purchase #4	$94.87	10.599%	$104.9253	$104.93	$104.95	$104.90
Purchase #5	$120.53	13.526%	$136.8329	$136.83	$136.85	$136.80
Purchase #6	$91.38	7.669%	$98.3879	$98.39	$98.40	$98.40
Purchase #7	$250.26	3.378%	$258.7138	$258.71	$258.70	$258.70
7 purchase totals =	$1,177.72		$1,255.0446	$1,255.05	$1,255.10	$1,255.00