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	$98.35	7.609%	$105.8335	$105.83	$105.85	$105.80
Purchase #2	$219.27	9.815%	$240.7914	$240.79	$240.80	$240.80
Purchase #3	$165.67	4.513%	$173.1467	$173.15	$173.15	$173.10
Purchase #4	$242.90	10.357%	$268.0572	$268.06	$268.05	$268.10
Purchase #5	$108.93	3.833%	$113.1053	$113.11	$113.10	$113.10
Purchase #6	$32.82	3.531%	$33.9789	$33.98	$34.00	$34.00
Purchase #7	$9.39	10.684%	$10.3932	$10.39	$10.40	$10.40
7 purchase totals =	$877.33		$945.3062	$945.31	$945.35	$945.30