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	$99.66	11.621%	$111.2415	$111.24	$111.25	$111.20
Purchase #2	$19.51	12.466%	$21.9421	$21.94	$21.95	$21.90
Purchase #3	$101.29	11.220%	$112.6547	$112.65	$112.65	$112.70
Purchase #4	$174.50	9.220%	$190.5889	$190.59	$190.60	$190.60
Purchase #5	$151.74	6.784%	$162.034	$162.03	$162.05	$162.00
Purchase #6	$236.45	5.379%	$249.1686	$249.17	$249.15	$249.20
Purchase #7	$236.38	12.381%	$265.6462	$265.65	$265.65	$265.60
7 purchase totals =	$1,019.53		$1,113.2760	$1,113.27	$1,113.30	$1,113.20