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	$159.47	9.512%	$174.6388	$174.64	$174.65	$174.60
Purchase #2	$158.70	12.169%	$178.0122	$178.01	$178.00	$178.00
Purchase #3	$172.88	5.335%	$182.1031	$182.10	$182.10	$182.10
Purchase #4	$21.89	11.700%	$24.4511	$24.45	$24.45	$24.50
Purchase #5	$134.53	12.579%	$151.4525	$151.45	$151.45	$151.50
Purchase #6	$77.78	11.831%	$86.9822	$86.98	$87.00	$87.00
Purchase #7	$53.57	5.152%	$56.3299	$56.33	$56.35	$56.30
7 purchase totals =	$778.82		$853.9698	$853.96	$854.00	$854.00