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	$87.34	3.310%	$90.231	$90.23	$90.25	$90.20
Purchase #2	$247.80	13.310%	$280.7822	$280.78	$280.80	$280.80
Purchase #3	$215.55	6.783%	$230.1708	$230.17	$230.15	$230.20
Purchase #4	$14.45	6.602%	$15.404	$15.40	$15.40	$15.40
Purchase #5	$87.65	5.158%	$92.171	$92.17	$92.15	$92.20
Purchase #6	$132.29	8.146%	$143.0663	$143.07	$143.05	$143.10
Purchase #7	$228.30	9.442%	$249.8561	$249.86	$249.85	$249.90
7 purchase totals =	$1,013.38		$1,101.6814	$1,101.68	$1,101.65	$1,101.80