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	$191.76	12.385%	$215.5095	$215.51	$215.50	$215.50
Purchase #2	$40.74	4.541%	$42.59	$42.59	$42.60	$42.60
Purchase #3	$13.39	4.676%	$14.0161	$14.02	$14.00	$14.00
Purchase #4	$72.99	11.361%	$81.2824	$81.28	$81.30	$81.30
Purchase #5	$41.84	5.712%	$44.2299	$44.23	$44.25	$44.20
Purchase #6	$144.86	6.613%	$154.4396	$154.44	$154.45	$154.40
Purchase #7	$29.85	10.584%	$33.0093	$33.01	$33.00	$33.00
7 purchase totals =	$535.43		$585.0768	$585.08	$585.10	$585.00