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	$146.47	8.535%	$158.9712	$158.97	$158.95	$159.00
Purchase #2	$239.92	11.479%	$267.4604	$267.46	$267.45	$267.50
Purchase #3	$131.70	8.665%	$143.1118	$143.11	$143.10	$143.10
Purchase #4	$47.90	11.859%	$53.5805	$53.58	$53.60	$53.60
Purchase #5	$46.57	11.471%	$51.912	$51.91	$51.90	$51.90
Purchase #6	$89.34	5.223%	$94.0062	$94.01	$94.00	$94.00
Purchase #7	$134.67	4.811%	$141.149	$141.15	$141.15	$141.10
7 purchase totals =	$836.57		$910.1911	$910.19	$910.15	$910.20