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	$88.32	5.413%	$93.1008	$93.10	$93.10	$93.10
Purchase #2	$75.47	10.655%	$83.5113	$83.51	$83.50	$83.50
Purchase #3	$243.83	7.246%	$261.4979	$261.50	$261.50	$261.50
Purchase #4	$130.89	10.258%	$144.3167	$144.32	$144.30	$144.30
Purchase #5	$96.82	7.132%	$103.7252	$103.73	$103.75	$103.70
Purchase #6	$150.45	5.183%	$158.2478	$158.25	$158.25	$158.20
Purchase #7	$215.75	12.153%	$241.9701	$241.97	$241.95	$242.00
7 purchase totals =	$1,001.53		$1,086.3698	$1,086.38	$1,086.35	$1,086.30