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	$228.94	4.758%	$239.833	$239.83	$239.85	$239.80
Purchase #2	$138.63	13.683%	$157.5987	$157.60	$157.60	$157.60
Purchase #3	$55.82	6.269%	$59.3194	$59.32	$59.30	$59.30
Purchase #4	$174.61	4.333%	$182.1759	$182.18	$182.20	$182.20
Purchase #5	$224.59	9.650%	$246.2629	$246.26	$246.25	$246.30
Purchase #6	$132.82	9.665%	$145.6571	$145.66	$145.65	$145.70
Purchase #7	$105.78	6.599%	$112.7604	$112.76	$112.75	$112.80
7 purchase totals =	$1,061.19		$1,143.6074	$1,143.61	$1,143.60	$1,143.70