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	$233.35	7.528%	$250.9166	$250.92	$250.90	$250.90
Purchase #2	$99.99	5.178%	$105.1675	$105.17	$105.15	$105.20
Purchase #3	$214.90	5.133%	$225.9308	$225.93	$225.95	$225.90
Purchase #4	$109.49	7.868%	$118.1047	$118.10	$118.10	$118.10
Purchase #5	$139.35	4.404%	$145.487	$145.49	$145.50	$145.50
Purchase #6	$12.51	13.291%	$14.1727	$14.17	$14.15	$14.20
Purchase #7	$241.64	3.229%	$249.4426	$249.44	$249.45	$249.40
7 purchase totals =	$1,051.23		$1,109.2219	$1,109.22	$1,109.20	$1,109.20