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	$230.48	13.650%	$261.9405	$261.94	$261.95	$261.90
Purchase #2	$236.89	13.119%	$267.9676	$267.97	$267.95	$268.00
Purchase #3	$145.83	5.343%	$153.6217	$153.62	$153.60	$153.60
Purchase #4	$19.42	5.648%	$20.5168	$20.52	$20.50	$20.50
Purchase #5	$121.56	10.517%	$134.3445	$134.34	$134.35	$134.30
Purchase #6	$118.83	4.151%	$123.7626	$123.76	$123.75	$123.80
Purchase #7	$26.73	11.584%	$29.8264	$29.83	$29.85	$29.80
7 purchase totals =	$899.74		$991.9801	$991.98	$991.95	$991.90