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	$89.90	6.540%	$95.7795	$95.78	$95.80	$95.80
Purchase #2	$19.43	12.317%	$21.8232	$21.82	$21.80	$21.80
Purchase #3	$180.65	10.866%	$200.2794	$200.28	$200.30	$200.30
Purchase #4	$82.94	4.281%	$86.4907	$86.49	$86.50	$86.50
Purchase #5	$175.47	13.284%	$198.7794	$198.78	$198.80	$198.80
Purchase #6	$162.94	6.113%	$172.9005	$172.90	$172.90	$172.90
Purchase #7	$159.87	11.446%	$178.1687	$178.17	$178.15	$178.20
7 purchase totals =	$871.20		$954.2214	$954.22	$954.25	$954.30