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	$66.77	3.760%	$69.2806	$69.28	$69.30	$69.30
Purchase #2	$80.73	11.848%	$90.2949	$90.29	$90.30	$90.30
Purchase #3	$90.30	4.707%	$94.5504	$94.55	$94.55	$94.60
Purchase #4	$75.99	7.604%	$81.7683	$81.77	$81.75	$81.80
Purchase #5	$175.89	11.689%	$196.4498	$196.45	$196.45	$196.40
Purchase #6	$43.26	13.848%	$49.2506	$49.25	$49.25	$49.30
Purchase #7	$95.48	7.493%	$102.6343	$102.63	$102.65	$102.60
7 purchase totals =	$628.42		$684.2289	$684.22	$684.25	$684.30