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	$106.80	5.122%	$112.2703	$112.27	$112.25	$112.30
Purchase #2	$192.33	13.640%	$218.5638	$218.56	$218.55	$218.60
Purchase #3	$140.61	12.823%	$158.6404	$158.64	$158.65	$158.60
Purchase #4	$122.94	3.795%	$127.6056	$127.61	$127.60	$127.60
Purchase #5	$135.39	9.509%	$148.2642	$148.26	$148.25	$148.30
Purchase #6	$208.25	11.525%	$232.2508	$232.25	$232.25	$232.30
Purchase #7	$90.56	13.160%	$102.4777	$102.48	$102.50	$102.50
7 purchase totals =	$996.88		$1,100.0728	$1,100.07	$1,100.05	$1,100.20