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	$162.52	10.668%	$179.8576	$179.86	$179.85	$179.90
Purchase #2	$157.43	13.207%	$178.2218	$178.22	$178.20	$178.20
Purchase #3	$133.36	13.419%	$151.2556	$151.26	$151.25	$151.30
Purchase #4	$100.36	9.223%	$109.6162	$109.62	$109.60	$109.60
Purchase #5	$131.68	13.143%	$148.9867	$148.99	$149.00	$149.00
Purchase #6	$66.75	7.232%	$71.5774	$71.58	$71.60	$71.60
Purchase #7	$42.88	7.239%	$45.9841	$45.98	$46.00	$46.00
7 purchase totals =	$794.98		$885.4994	$885.51	$885.50	$885.60