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	$246.70	3.524%	$255.3937	$255.39	$255.40	$255.40
Purchase #2	$42.30	5.458%	$44.6087	$44.61	$44.60	$44.60
Purchase #3	$103.81	10.137%	$114.3332	$114.33	$114.35	$114.30
Purchase #4	$107.93	3.707%	$111.931	$111.93	$111.95	$111.90
Purchase #5	$127.86	8.361%	$138.5504	$138.55	$138.55	$138.60
Purchase #6	$186.70	7.366%	$200.4523	$200.45	$200.45	$200.50
Purchase #7	$53.93	7.316%	$57.8755	$57.88	$57.90	$57.90
7 purchase totals =	$869.23		$923.1448	$923.14	$923.20	$923.20