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	$153.72	12.405%	$172.789	$172.79	$172.80	$172.80
Purchase #2	$164.66	3.195%	$169.9209	$169.92	$169.90	$169.90
Purchase #3	$72.43	4.357%	$75.5858	$75.59	$75.60	$75.60
Purchase #4	$248.67	3.558%	$257.5177	$257.52	$257.50	$257.50
Purchase #5	$201.26	4.577%	$210.4717	$210.47	$210.45	$210.50
Purchase #6	$36.89	6.540%	$39.3026	$39.30	$39.30	$39.30
Purchase #7	$162.59	5.855%	$172.1096	$172.11	$172.10	$172.10
7 purchase totals =	$1,040.22		$1,097.6973	$1,097.70	$1,097.65	$1,097.70