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	$94.69	5.426%	$99.8279	$99.83	$99.85	$99.80
Purchase #2	$197.77	13.296%	$224.0655	$224.07	$224.05	$224.10
Purchase #3	$242.41	7.178%	$259.8102	$259.81	$259.80	$259.80
Purchase #4	$167.69	13.643%	$190.5679	$190.57	$190.55	$190.60
Purchase #5	$228.87	11.480%	$255.1443	$255.14	$255.15	$255.10
Purchase #6	$40.54	8.553%	$44.0074	$44.01	$44.00	$44.00
Purchase #7	$87.98	13.191%	$99.5854	$99.59	$99.60	$99.60
7 purchase totals =	$1,059.95		$1,173.0086	$1,173.02	$1,173.00	$1,173.00