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	$99.55	8.173%	$107.6862	$107.69	$107.70	$107.70
Purchase #2	$167.64	13.562%	$190.3753	$190.38	$190.40	$190.40
Purchase #3	$11.35	3.229%	$11.7165	$11.72	$11.70	$11.70
Purchase #4	$115.65	13.504%	$131.2674	$131.27	$131.25	$131.30
Purchase #5	$112.26	13.496%	$127.4106	$127.41	$127.40	$127.40
Purchase #6	$183.79	10.709%	$203.4721	$203.47	$203.45	$203.50
Purchase #7	$171.39	11.206%	$190.596	$190.60	$190.60	$190.60
7 purchase totals =	$861.63		$962.5241	$962.54	$962.50	$962.60