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	$127.84	10.721%	$141.5457	$141.55	$141.55	$141.50
Purchase #2	$17.47	5.302%	$18.3963	$18.40	$18.40	$18.40
Purchase #3	$162.62	3.558%	$168.406	$168.41	$168.40	$168.40
Purchase #4	$123.92	7.582%	$133.3156	$133.32	$133.30	$133.30
Purchase #5	$32.56	8.284%	$35.2573	$35.26	$35.25	$35.30
Purchase #6	$68.57	5.634%	$72.4332	$72.43	$72.45	$72.40
Purchase #7	$34.65	11.352%	$38.5835	$38.58	$38.60	$38.60
7 purchase totals =	$567.63		$607.9376	$607.95	$607.95	$607.90