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	$169.35	7.359%	$181.8125	$181.81	$181.80	$181.80
Purchase #2	$91.76	4.365%	$95.7653	$95.77	$95.75	$95.80
Purchase #3	$133.31	9.613%	$146.1251	$146.13	$146.15	$146.10
Purchase #4	$216.85	13.452%	$246.0207	$246.02	$246.00	$246.00
Purchase #5	$161.68	12.738%	$182.2748	$182.27	$182.25	$182.30
Purchase #6	$126.61	13.806%	$144.0898	$144.09	$144.10	$144.10
Purchase #7	$91.95	12.435%	$103.384	$103.38	$103.40	$103.40
7 purchase totals =	$991.51		$1,099.4722	$1,099.47	$1,099.45	$1,099.50