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	$143.30	10.828%	$158.8165	$158.82	$158.80	$158.80
Purchase #2	$169.72	8.109%	$183.4826	$183.48	$183.50	$183.50
Purchase #3	$163.99	3.520%	$169.7624	$169.76	$169.75	$169.80
Purchase #4	$141.73	10.397%	$156.4657	$156.47	$156.45	$156.50
Purchase #5	$50.34	5.295%	$53.0055	$53.01	$53.00	$53.00
Purchase #6	$243.72	3.718%	$252.7815	$252.78	$252.80	$252.80
Purchase #7	$30.50	7.533%	$32.7976	$32.80	$32.80	$32.80
7 purchase totals =	$943.30		$1,007.1118	$1,007.12	$1,007.10	$1,007.20