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	$57.88	6.826%	$61.8309	$61.83	$61.85	$61.80
Purchase #2	$148.99	13.829%	$169.5938	$169.59	$169.60	$169.60
Purchase #3	$44.36	8.413%	$48.092	$48.09	$48.10	$48.10
Purchase #4	$222.65	10.307%	$245.5985	$245.60	$245.60	$245.60
Purchase #5	$223.52	8.681%	$242.9238	$242.92	$242.90	$242.90
Purchase #6	$228.97	8.116%	$247.5532	$247.55	$247.55	$247.60
Purchase #7	$107.32	4.388%	$112.0292	$112.03	$112.05	$112.00
7 purchase totals =	$1,033.69		$1,127.6214	$1,127.61	$1,127.65	$1,127.60