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	$97.33	3.636%	$100.8689	$100.87	$100.85	$100.90
Purchase #2	$72.59	3.243%	$74.9441	$74.94	$74.95	$74.90
Purchase #3	$97.77	4.219%	$101.8949	$101.89	$101.90	$101.90
Purchase #4	$250.33	8.874%	$272.5443	$272.54	$272.55	$272.50
Purchase #5	$211.83	8.716%	$230.2931	$230.29	$230.30	$230.30
Purchase #6	$152.52	4.429%	$159.2751	$159.28	$159.30	$159.30
Purchase #7	$221.47	11.711%	$247.4064	$247.41	$247.40	$247.40
7 purchase totals =	$1,103.84		$1,187.2268	$1,187.22	$1,187.25	$1,187.20