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	$10.64	6.614%	$11.3437	$11.34	$11.35	$11.30
Purchase #2	$50.60	13.327%	$57.3435	$57.34	$57.35	$57.30
Purchase #3	$202.55	3.221%	$209.0741	$209.07	$209.05	$209.10
Purchase #4	$241.43	8.775%	$262.6155	$262.62	$262.60	$262.60
Purchase #5	$36.39	11.109%	$40.4326	$40.43	$40.45	$40.40
Purchase #6	$138.50	4.776%	$145.1148	$145.11	$145.10	$145.10
Purchase #7	$85.94	5.381%	$90.5644	$90.56	$90.55	$90.60
7 purchase totals =	$766.05		$816.4886	$816.47	$816.45	$816.40