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	$7.30	10.532%	$8.0688	$8.07	$8.05	$8.10
Purchase #2	$83.72	6.816%	$89.4264	$89.43	$89.45	$89.40
Purchase #3	$230.94	6.508%	$245.9696	$245.97	$245.95	$246.00
Purchase #4	$66.41	12.775%	$74.8939	$74.89	$74.90	$74.90
Purchase #5	$186.93	5.307%	$196.8504	$196.85	$196.85	$196.90
Purchase #6	$50.75	13.483%	$57.5926	$57.59	$57.60	$57.60
Purchase #7	$247.90	12.585%	$279.0982	$279.10	$279.10	$279.10
7 purchase totals =	$873.95		$951.8999	$951.90	$951.90	$952.00