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	$92.50	8.675%	$100.5244	$100.52	$100.50	$100.50
Purchase #2	$86.74	4.159%	$90.3475	$90.35	$90.35	$90.30
Purchase #3	$134.63	9.373%	$147.2489	$147.25	$147.25	$147.20
Purchase #4	$151.49	10.307%	$167.1041	$167.10	$167.10	$167.10
Purchase #5	$113.60	8.491%	$123.2458	$123.25	$123.25	$123.20
Purchase #6	$49.48	10.497%	$54.6739	$54.67	$54.65	$54.70
Purchase #7	$198.78	7.189%	$213.0703	$213.07	$213.05	$213.10
7 purchase totals =	$827.22		$896.2149	$896.21	$896.15	$896.10