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	$30.56	5.216%	$32.154	$32.15	$32.15	$32.20
Purchase #2	$6.89	11.564%	$7.6868	$7.69	$7.70	$7.70
Purchase #3	$14.56	9.351%	$15.9215	$15.92	$15.90	$15.90
Purchase #4	$174.71	9.109%	$190.6243	$190.62	$190.60	$190.60
Purchase #5	$50.42	5.594%	$53.2405	$53.24	$53.25	$53.20
Purchase #6	$169.30	4.523%	$176.9574	$176.96	$176.95	$177.00
Purchase #7	$105.30	7.205%	$112.8869	$112.89	$112.90	$112.90
7 purchase totals =	$551.74		$589.4714	$589.47	$589.45	$589.50