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	$153.79	7.678%	$165.598	$165.60	$165.60	$165.60
Purchase #2	$126.28	10.655%	$139.7351	$139.74	$139.75	$139.70
Purchase #3	$89.82	5.788%	$95.0188	$95.02	$95.00	$95.00
Purchase #4	$229.77	11.762%	$256.7955	$256.80	$256.80	$256.80
Purchase #5	$165.44	9.680%	$181.4546	$181.45	$181.45	$181.50
Purchase #6	$147.83	8.388%	$160.23	$160.23	$160.25	$160.20
Purchase #7	$86.87	12.301%	$97.5559	$97.56	$97.55	$97.60
7 purchase totals =	$999.80		$1,096.3879	$1,096.40	$1,096.40	$1,096.40