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	$22.38	8.364%	$24.2519	$24.25	$24.25	$24.30
Purchase #2	$148.85	6.217%	$158.104	$158.10	$158.10	$158.10
Purchase #3	$214.33	12.817%	$241.8007	$241.80	$241.80	$241.80
Purchase #4	$42.42	8.719%	$46.1186	$46.12	$46.10	$46.10
Purchase #5	$82.34	9.738%	$90.3583	$90.36	$90.35	$90.40
Purchase #6	$34.88	12.757%	$39.3296	$39.33	$39.35	$39.30
Purchase #7	$99.47	10.858%	$110.2705	$110.27	$110.25	$110.30
7 purchase totals =	$644.67		$710.2336	$710.23	$710.20	$710.30