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	$220.63	3.718%	$228.833	$228.83	$228.85	$228.80
Purchase #2	$189.89	10.796%	$210.3905	$210.39	$210.40	$210.40
Purchase #3	$53.38	10.406%	$58.9347	$58.93	$58.95	$58.90
Purchase #4	$172.40	5.353%	$181.6286	$181.63	$181.65	$181.60
Purchase #5	$20.63	4.863%	$21.6332	$21.63	$21.65	$21.60
Purchase #6	$66.56	7.644%	$71.6478	$71.65	$71.65	$71.60
Purchase #7	$28.83	13.504%	$32.7232	$32.72	$32.70	$32.70
7 purchase totals =	$752.32		$805.7910	$805.78	$805.85	$805.60