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	$171.83	5.502%	$181.2841	$181.28	$181.30	$181.30
Purchase #2	$103.87	3.788%	$107.8046	$107.80	$107.80	$107.80
Purchase #3	$158.45	12.370%	$178.0503	$178.05	$178.05	$178.10
Purchase #4	$100.27	11.363%	$111.6637	$111.66	$111.65	$111.70
Purchase #5	$53.53	11.421%	$59.6437	$59.64	$59.65	$59.60
Purchase #6	$201.42	12.258%	$226.1101	$226.11	$226.10	$226.10
Purchase #7	$153.66	8.602%	$166.8778	$166.88	$166.90	$166.90
7 purchase totals =	$943.03		$1,031.4343	$1,031.42	$1,031.45	$1,031.50