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	$207.87	8.490%	$225.5182	$225.52	$225.50	$225.50
Purchase #2	$80.41	5.848%	$85.1124	$85.11	$85.10	$85.10
Purchase #3	$110.41	5.451%	$116.4284	$116.43	$116.45	$116.40
Purchase #4	$103.69	9.511%	$113.552	$113.55	$113.55	$113.60
Purchase #5	$72.92	7.359%	$78.2862	$78.29	$78.30	$78.30
Purchase #6	$244.68	4.328%	$255.2698	$255.27	$255.25	$255.30
Purchase #7	$235.84	5.431%	$248.6485	$248.65	$248.65	$248.60
7 purchase totals =	$1,055.82		$1,122.8155	$1,122.82	$1,122.80	$1,122.80