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	$123.58	7.423%	$132.7533	$132.75	$132.75	$132.80
Purchase #2	$45.89	9.784%	$50.3799	$50.38	$50.40	$50.40
Purchase #3	$240.27	13.493%	$272.6896	$272.69	$272.70	$272.70
Purchase #4	$199.96	8.284%	$216.5247	$216.52	$216.50	$216.50
Purchase #5	$38.77	8.653%	$42.1248	$42.12	$42.10	$42.10
Purchase #6	$169.30	3.574%	$175.3508	$175.35	$175.35	$175.40
Purchase #7	$177.77	5.632%	$187.782	$187.78	$187.80	$187.80
7 purchase totals =	$995.54		$1,077.6051	$1,077.59	$1,077.60	$1,077.70