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	$156.95	6.383%	$166.9681	$166.97	$166.95	$167.00
Purchase #2	$119.88	7.126%	$128.4226	$128.42	$128.40	$128.40
Purchase #3	$59.55	13.541%	$67.6137	$67.61	$67.60	$67.60
Purchase #4	$32.87	4.745%	$34.4297	$34.43	$34.45	$34.40
Purchase #5	$201.44	10.560%	$222.7121	$222.71	$222.70	$222.70
Purchase #6	$104.96	6.399%	$111.6764	$111.68	$111.70	$111.70
Purchase #7	$173.96	3.207%	$179.5389	$179.54	$179.55	$179.50
7 purchase totals =	$849.61		$911.3615	$911.36	$911.35	$911.30