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	$10.59	3.312%	$10.9407	$10.94	$10.95	$10.90
Purchase #2	$104.35	11.764%	$116.6257	$116.63	$116.65	$116.60
Purchase #3	$112.98	3.854%	$117.3342	$117.33	$117.35	$117.30
Purchase #4	$99.39	12.574%	$111.8873	$111.89	$111.90	$111.90
Purchase #5	$151.69	11.363%	$168.9265	$168.93	$168.95	$168.90
Purchase #6	$53.89	10.200%	$59.3868	$59.39	$59.40	$59.40
Purchase #7	$157.66	12.149%	$176.8141	$176.81	$176.80	$176.80
7 purchase totals =	$690.55		$761.9153	$761.92	$762.00	$761.80