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	$146.85	4.408%	$153.3231	$153.32	$153.30	$153.30
Purchase #2	$163.95	13.204%	$185.598	$185.60	$185.60	$185.60
Purchase #3	$33.96	5.366%	$35.7823	$35.78	$35.80	$35.80
Purchase #4	$88.85	11.725%	$99.2677	$99.27	$99.25	$99.30
Purchase #5	$97.38	4.126%	$101.3979	$101.40	$101.40	$101.40
Purchase #6	$149.59	8.536%	$162.359	$162.36	$162.35	$162.40
Purchase #7	$234.41	7.456%	$251.8876	$251.89	$251.90	$251.90
7 purchase totals =	$914.99		$989.6156	$989.62	$989.60	$989.70