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	$35.94	7.167%	$38.5158	$38.52	$38.50	$38.50
Purchase #2	$35.32	6.122%	$37.4823	$37.48	$37.50	$37.50
Purchase #3	$103.47	5.390%	$109.047	$109.05	$109.05	$109.00
Purchase #4	$211.90	7.529%	$227.854	$227.85	$227.85	$227.90
Purchase #5	$14.69	3.767%	$15.2434	$15.24	$15.25	$15.20
Purchase #6	$58.87	6.602%	$62.7566	$62.76	$62.75	$62.80
Purchase #7	$235.80	6.140%	$250.2781	$250.28	$250.30	$250.30
7 purchase totals =	$695.99		$741.1772	$741.18	$741.20	$741.20