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	$231.97	13.167%	$262.5135	$262.51	$262.50	$262.50
Purchase #2	$126.50	13.239%	$143.2473	$143.25	$143.25	$143.20
Purchase #3	$242.90	7.784%	$261.8073	$261.81	$261.80	$261.80
Purchase #4	$63.72	3.134%	$65.717	$65.72	$65.70	$65.70
Purchase #5	$142.87	5.430%	$150.6278	$150.63	$150.65	$150.60
Purchase #6	$140.71	3.236%	$145.2634	$145.26	$145.25	$145.30
Purchase #7	$107.30	8.820%	$116.7639	$116.76	$116.75	$116.80
7 purchase totals =	$1,055.97		$1,145.9402	$1,145.94	$1,145.90	$1,145.90