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	$47.33	11.754%	$52.8932	$52.89	$52.90	$52.90
Purchase #2	$83.79	13.545%	$95.1394	$95.14	$95.15	$95.10
Purchase #3	$242.27	5.732%	$256.1569	$256.16	$256.15	$256.20
Purchase #4	$107.59	3.409%	$111.2577	$111.26	$111.25	$111.30
Purchase #5	$196.42	10.133%	$216.3232	$216.32	$216.30	$216.30
Purchase #6	$132.98	4.165%	$138.5186	$138.52	$138.50	$138.50
Purchase #7	$224.88	11.148%	$249.9496	$249.95	$249.95	$249.90
7 purchase totals =	$1,035.26		$1,120.2386	$1,120.24	$1,120.20	$1,120.20