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	$162.83	11.262%	$181.1679	$181.17	$181.15	$181.20
Purchase #2	$248.31	5.750%	$262.5878	$262.59	$262.60	$262.60
Purchase #3	$109.84	13.275%	$124.4213	$124.42	$124.40	$124.40
Purchase #4	$64.78	9.373%	$70.8518	$70.85	$70.85	$70.90
Purchase #5	$96.86	8.593%	$105.1832	$105.18	$105.20	$105.20
Purchase #6	$118.61	11.793%	$132.5977	$132.60	$132.60	$132.60
Purchase #7	$171.92	9.576%	$188.3831	$188.38	$188.40	$188.40
7 purchase totals =	$973.15		$1,065.1928	$1,065.19	$1,065.20	$1,065.30