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	$175.45	7.598%	$188.7807	$188.78	$188.80	$188.80
Purchase #2	$220.59	3.264%	$227.7901	$227.79	$227.80	$227.80
Purchase #3	$49.79	5.524%	$52.5404	$52.54	$52.55	$52.50
Purchase #4	$88.31	7.739%	$95.1443	$95.14	$95.15	$95.10
Purchase #5	$96.87	9.238%	$105.8189	$105.82	$105.80	$105.80
Purchase #6	$138.28	8.778%	$150.4182	$150.42	$150.40	$150.40
Purchase #7	$132.40	11.826%	$148.0576	$148.06	$148.05	$148.10
7 purchase totals =	$901.69		$968.5502	$968.55	$968.55	$968.50