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	$141.39	7.520%	$152.0225	$152.02	$152.00	$152.00
Purchase #2	$62.49	6.307%	$66.4312	$66.43	$66.45	$66.40
Purchase #3	$65.62	11.334%	$73.0574	$73.06	$73.05	$73.10
Purchase #4	$5.59	13.509%	$6.3452	$6.35	$6.35	$6.30
Purchase #5	$106.49	6.855%	$113.7899	$113.79	$113.80	$113.80
Purchase #6	$6.38	13.694%	$7.2537	$7.25	$7.25	$7.30
Purchase #7	$94.89	5.782%	$100.3765	$100.38	$100.40	$100.40
7 purchase totals =	$482.85		$519.2764	$519.28	$519.30	$519.30