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	$215.69	6.317%	$229.3151	$229.32	$229.30	$229.30
Purchase #2	$230.30	3.604%	$238.6	$238.60	$238.60	$238.60
Purchase #3	$54.85	4.624%	$57.3863	$57.39	$57.40	$57.40
Purchase #4	$72.60	13.533%	$82.425	$82.43	$82.45	$82.40
Purchase #5	$242.29	12.532%	$272.6538	$272.65	$272.65	$272.70
Purchase #6	$14.37	13.709%	$16.34	$16.34	$16.35	$16.30
Purchase #7	$51.61	6.439%	$54.9332	$54.93	$54.95	$54.90
7 purchase totals =	$881.71		$951.6534	$951.66	$951.70	$951.60