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	$123.56	7.491%	$132.8159	$132.82	$132.80	$132.80
Purchase #2	$82.41	3.319%	$85.1452	$85.15	$85.15	$85.10
Purchase #3	$29.41	10.208%	$32.4122	$32.41	$32.40	$32.40
Purchase #4	$209.66	5.530%	$221.2542	$221.25	$221.25	$221.30
Purchase #5	$126.73	10.671%	$140.2534	$140.25	$140.25	$140.30
Purchase #6	$134.62	3.351%	$139.1311	$139.13	$139.15	$139.10
Purchase #7	$12.58	13.541%	$14.2835	$14.28	$14.30	$14.30
7 purchase totals =	$718.97		$765.2955	$765.29	$765.30	$765.30