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	$104.33	6.859%	$111.486	$111.49	$111.50	$111.50
Purchase #2	$56.73	5.671%	$59.9472	$59.95	$59.95	$59.90
Purchase #3	$136.76	9.575%	$149.8548	$149.85	$149.85	$149.90
Purchase #4	$16.65	7.210%	$17.8505	$17.85	$17.85	$17.90
Purchase #5	$101.89	5.672%	$107.6692	$107.67	$107.65	$107.70
Purchase #6	$190.46	3.290%	$196.7261	$196.73	$196.75	$196.70
Purchase #7	$71.41	11.187%	$79.3986	$79.40	$79.40	$79.40
7 purchase totals =	$678.23		$722.9324	$722.94	$722.95	$723.00