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	$65.74	12.304%	$73.8286	$73.83	$73.85	$73.80
Purchase #2	$144.82	5.623%	$152.9632	$152.96	$152.95	$153.00
Purchase #3	$132.97	11.629%	$148.4331	$148.43	$148.45	$148.40
Purchase #4	$47.69	12.190%	$53.5034	$53.50	$53.50	$53.50
Purchase #5	$14.72	3.549%	$15.2424	$15.24	$15.25	$15.20
Purchase #6	$57.65	3.738%	$59.805	$59.81	$59.80	$59.80
Purchase #7	$216.97	13.406%	$246.057	$246.06	$246.05	$246.10
7 purchase totals =	$680.56		$749.8327	$749.83	$749.85	$749.80