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	$148.71	7.218%	$159.4439	$159.44	$159.45	$159.40
Purchase #2	$12.72	4.527%	$13.2958	$13.30	$13.30	$13.30
Purchase #3	$130.93	13.514%	$148.6239	$148.62	$148.60	$148.60
Purchase #4	$54.60	12.598%	$61.4785	$61.48	$61.50	$61.50
Purchase #5	$206.27	10.549%	$228.0294	$228.03	$228.05	$228.00
Purchase #6	$211.71	6.317%	$225.0837	$225.08	$225.10	$225.10
Purchase #7	$91.39	9.522%	$100.0922	$100.09	$100.10	$100.10
7 purchase totals =	$856.33		$936.0474	$936.04	$936.10	$936.00