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	$181.98	3.624%	$188.575	$188.58	$188.60	$188.60
Purchase #2	$28.56	6.872%	$30.5226	$30.52	$30.50	$30.50
Purchase #3	$134.43	13.866%	$153.0701	$153.07	$153.05	$153.10
Purchase #4	$76.35	11.380%	$85.0386	$85.04	$85.05	$85.00
Purchase #5	$38.81	5.286%	$40.8615	$40.86	$40.85	$40.90
Purchase #6	$246.25	9.846%	$270.4958	$270.50	$270.50	$270.50
Purchase #7	$175.53	7.273%	$188.2963	$188.30	$188.30	$188.30
7 purchase totals =	$881.91		$956.8599	$956.87	$956.85	$956.90