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	$95.87	12.158%	$107.5259	$107.53	$107.55	$107.50
Purchase #2	$150.85	10.362%	$166.4811	$166.48	$166.50	$166.50
Purchase #3	$56.39	5.536%	$59.5118	$59.51	$59.50	$59.50
Purchase #4	$20.26	4.299%	$21.131	$21.13	$21.15	$21.10
Purchase #5	$48.61	8.608%	$52.7943	$52.79	$52.80	$52.80
Purchase #6	$141.72	4.799%	$148.5211	$148.52	$148.50	$148.50
Purchase #7	$138.32	11.590%	$154.3513	$154.35	$154.35	$154.40
7 purchase totals =	$652.02		$710.3165	$710.31	$710.35	$710.30