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	$185.68	4.423%	$193.8926	$193.89	$193.90	$193.90
Purchase #2	$126.77	8.440%	$137.4694	$137.47	$137.45	$137.50
Purchase #3	$54.97	4.781%	$57.5981	$57.60	$57.60	$57.60
Purchase #4	$238.35	7.240%	$255.6065	$255.61	$255.60	$255.60
Purchase #5	$160.78	8.599%	$174.6055	$174.61	$174.60	$174.60
Purchase #6	$120.49	9.650%	$132.1173	$132.12	$132.10	$132.10
Purchase #7	$24.49	13.176%	$27.7168	$27.72	$27.70	$27.70
7 purchase totals =	$911.53		$979.0062	$979.02	$978.95	$979.00