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	$226.85	4.674%	$237.453	$237.45	$237.45	$237.50
Purchase #2	$78.60	4.503%	$82.1394	$82.14	$82.15	$82.10
Purchase #3	$123.47	3.119%	$127.321	$127.32	$127.30	$127.30
Purchase #4	$214.41	9.614%	$235.0234	$235.02	$235.00	$235.00
Purchase #5	$35.97	4.596%	$37.6232	$37.62	$37.60	$37.60
Purchase #6	$143.72	11.308%	$159.9719	$159.97	$159.95	$160.00
Purchase #7	$161.75	9.742%	$177.5077	$177.51	$177.50	$177.50
7 purchase totals =	$984.77		$1,057.0396	$1,057.03	$1,056.95	$1,057.00