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	$215.56	13.610%	$244.8977	$244.90	$244.90	$244.90
Purchase #2	$86.47	4.255%	$90.1493	$90.15	$90.15	$90.10
Purchase #3	$215.75	4.230%	$224.8762	$224.88	$224.90	$224.90
Purchase #4	$85.56	11.677%	$95.5508	$95.55	$95.55	$95.60
Purchase #5	$61.82	5.451%	$65.1898	$65.19	$65.20	$65.20
Purchase #6	$243.72	6.198%	$258.8258	$258.83	$258.85	$258.80
Purchase #7	$21.70	7.528%	$23.3336	$23.33	$23.35	$23.30
7 purchase totals =	$930.58		$1,002.8232	$1,002.83	$1,002.90	$1,002.80