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	$174.80	5.604%	$184.5958	$184.60	$184.60	$184.60
Purchase #2	$54.53	13.738%	$62.0213	$62.02	$62.00	$62.00
Purchase #3	$45.73	10.282%	$50.432	$50.43	$50.45	$50.40
Purchase #4	$70.58	11.383%	$78.6141	$78.61	$78.60	$78.60
Purchase #5	$46.77	7.652%	$50.3488	$50.35	$50.35	$50.30
Purchase #6	$201.78	10.171%	$222.303	$222.30	$222.30	$222.30
Purchase #7	$166.73	12.208%	$187.0844	$187.08	$187.10	$187.10
7 purchase totals =	$760.92		$835.3994	$835.39	$835.40	$835.30