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	$128.42	7.655%	$138.2506	$138.25	$138.25	$138.30
Purchase #2	$189.77	5.687%	$200.5622	$200.56	$200.55	$200.60
Purchase #3	$247.40	10.684%	$273.8322	$273.83	$273.85	$273.80
Purchase #4	$132.58	13.648%	$150.6745	$150.67	$150.65	$150.70
Purchase #5	$162.78	3.127%	$167.8701	$167.87	$167.85	$167.90
Purchase #6	$116.85	3.513%	$120.9549	$120.95	$120.95	$121.00
Purchase #7	$146.45	10.771%	$162.2241	$162.22	$162.20	$162.20
7 purchase totals =	$1,124.25		$1,214.3686	$1,214.35	$1,214.30	$1,214.50