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	$116.95	5.554%	$123.4454	$123.45	$123.45	$123.40
Purchase #2	$48.42	11.224%	$53.8547	$53.85	$53.85	$53.90
Purchase #3	$193.68	3.568%	$200.5905	$200.59	$200.60	$200.60
Purchase #4	$134.70	3.511%	$139.4293	$139.43	$139.45	$139.40
Purchase #5	$48.86	6.488%	$52.03	$52.03	$52.05	$52.00
Purchase #6	$204.97	9.438%	$224.3151	$224.32	$224.30	$224.30
Purchase #7	$56.59	4.825%	$59.3205	$59.32	$59.30	$59.30
7 purchase totals =	$804.17		$852.9855	$852.99	$853.00	$852.90