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	$72.29	9.855%	$79.4142	$79.41	$79.40	$79.40
Purchase #2	$65.89	10.216%	$72.6213	$72.62	$72.60	$72.60
Purchase #3	$42.94	4.868%	$45.0303	$45.03	$45.05	$45.00
Purchase #4	$199.49	11.442%	$222.3156	$222.32	$222.30	$222.30
Purchase #5	$37.40	6.651%	$39.8875	$39.89	$39.90	$39.90
Purchase #6	$241.69	8.560%	$262.3787	$262.38	$262.40	$262.40
Purchase #7	$73.32	4.454%	$76.5857	$76.59	$76.60	$76.60
7 purchase totals =	$733.02		$798.2333	$798.24	$798.25	$798.20