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	$92.60	11.296%	$103.0601	$103.06	$103.05	$103.10
Purchase #2	$244.68	7.261%	$262.4462	$262.45	$262.45	$262.40
Purchase #3	$15.40	9.581%	$16.8755	$16.88	$16.90	$16.90
Purchase #4	$237.45	11.433%	$264.5977	$264.60	$264.60	$264.60
Purchase #5	$132.76	5.366%	$139.8839	$139.88	$139.90	$139.90
Purchase #6	$72.99	11.665%	$81.5043	$81.50	$81.50	$81.50
Purchase #7	$225.65	6.769%	$240.9242	$240.92	$240.90	$240.90
7 purchase totals =	$1,021.53		$1,109.2919	$1,109.29	$1,109.30	$1,109.30