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	$233.27	6.140%	$247.5928	$247.59	$247.60	$247.60
Purchase #2	$81.93	10.622%	$90.6326	$90.63	$90.65	$90.60
Purchase #3	$158.42	11.326%	$176.3626	$176.36	$176.35	$176.40
Purchase #4	$207.61	12.673%	$233.9204	$233.92	$233.90	$233.90
Purchase #5	$239.56	7.484%	$257.4887	$257.49	$257.50	$257.50
Purchase #6	$34.29	13.404%	$38.8862	$38.89	$38.90	$38.90
Purchase #7	$131.83	8.269%	$142.731	$142.73	$142.75	$142.70
7 purchase totals =	$1,086.91		$1,187.6143	$1,187.61	$1,187.65	$1,187.60