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	$41.64	8.854%	$45.3268	$45.33	$45.35	$45.30
Purchase #2	$58.41	3.574%	$60.4976	$60.50	$60.50	$60.50
Purchase #3	$13.61	13.456%	$15.4414	$15.44	$15.45	$15.40
Purchase #4	$56.41	9.169%	$61.5822	$61.58	$61.60	$61.60
Purchase #5	$241.79	8.721%	$262.8765	$262.88	$262.90	$262.90
Purchase #6	$139.47	10.122%	$153.5872	$153.59	$153.60	$153.60
Purchase #7	$216.82	3.258%	$223.884	$223.88	$223.90	$223.90
7 purchase totals =	$768.15		$823.1957	$823.20	$823.30	$823.20