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	$162.75	11.137%	$180.8755	$180.88	$180.90	$180.90
Purchase #2	$224.84	3.739%	$233.2468	$233.25	$233.25	$233.20
Purchase #3	$118.88	12.320%	$133.526	$133.53	$133.55	$133.50
Purchase #4	$76.94	8.642%	$83.5892	$83.59	$83.60	$83.60
Purchase #5	$89.45	7.160%	$95.8546	$95.85	$95.85	$95.90
Purchase #6	$99.48	5.720%	$105.1703	$105.17	$105.15	$105.20
Purchase #7	$152.52	13.265%	$172.7518	$172.75	$172.75	$172.80
7 purchase totals =	$924.86		$1,005.0142	$1,005.02	$1,005.05	$1,005.10