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	$219.59	8.581%	$238.433	$238.43	$238.45	$238.40
Purchase #2	$83.87	7.140%	$89.8583	$89.86	$89.85	$89.90
Purchase #3	$237.44	5.607%	$250.7533	$250.75	$250.75	$250.80
Purchase #4	$178.33	5.540%	$188.2095	$188.21	$188.20	$188.20
Purchase #5	$234.94	11.341%	$261.5845	$261.58	$261.60	$261.60
Purchase #6	$100.71	7.522%	$108.2854	$108.29	$108.30	$108.30
Purchase #7	$23.47	6.170%	$24.9181	$24.92	$24.90	$24.90
7 purchase totals =	$1,078.35		$1,162.0421	$1,162.04	$1,162.05	$1,162.10