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	$150.27	12.753%	$169.4339	$169.43	$169.45	$169.40
Purchase #2	$190.71	13.773%	$216.9765	$216.98	$217.00	$217.00
Purchase #3	$146.52	11.728%	$163.7039	$163.70	$163.70	$163.70
Purchase #4	$108.55	3.127%	$111.9444	$111.94	$111.95	$111.90
Purchase #5	$46.86	6.662%	$49.9818	$49.98	$50.00	$50.00
Purchase #6	$31.75	4.815%	$33.2788	$33.28	$33.30	$33.30
Purchase #7	$92.40	8.535%	$100.2863	$100.29	$100.30	$100.30
7 purchase totals =	$767.06		$845.6056	$845.60	$845.70	$845.60