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	$147.50	8.768%	$160.4328	$160.43	$160.45	$160.40
Purchase #2	$91.95	13.393%	$104.2649	$104.26	$104.25	$104.30
Purchase #3	$39.91	4.133%	$41.5595	$41.56	$41.55	$41.60
Purchase #4	$160.66	5.566%	$169.6023	$169.60	$169.60	$169.60
Purchase #5	$138.47	8.339%	$150.017	$150.02	$150.00	$150.00
Purchase #6	$216.53	12.763%	$244.1657	$244.17	$244.15	$244.20
Purchase #7	$138.59	7.400%	$148.8457	$148.85	$148.85	$148.80
7 purchase totals =	$933.61		$1,018.8879	$1,018.89	$1,018.85	$1,018.90