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	$247.47	6.650%	$263.9268	$263.93	$263.95	$263.90
Purchase #2	$126.28	9.495%	$138.2703	$138.27	$138.25	$138.30
Purchase #3	$92.48	4.316%	$96.4714	$96.47	$96.45	$96.50
Purchase #4	$193.98	5.506%	$204.6605	$204.66	$204.65	$204.70
Purchase #5	$109.85	8.307%	$118.9752	$118.98	$119.00	$119.00
Purchase #6	$72.31	8.342%	$78.3421	$78.34	$78.35	$78.30
Purchase #7	$238.27	7.273%	$255.5994	$255.60	$255.60	$255.60
7 purchase totals =	$1,080.64		$1,156.2457	$1,156.25	$1,156.25	$1,156.30