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	$234.45	3.103%	$241.725	$241.73	$241.75	$241.70
Purchase #2	$220.90	12.850%	$249.2857	$249.29	$249.30	$249.30
Purchase #3	$114.70	12.109%	$128.589	$128.59	$128.60	$128.60
Purchase #4	$51.92	3.112%	$53.5358	$53.54	$53.55	$53.50
Purchase #5	$11.52	7.860%	$12.4255	$12.43	$12.45	$12.40
Purchase #6	$7.94	8.157%	$8.5877	$8.59	$8.60	$8.60
Purchase #7	$151.77	13.511%	$172.2756	$172.28	$172.30	$172.30
7 purchase totals =	$793.20		$866.4243	$866.45	$866.55	$866.40