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	$205.93	3.610%	$213.3641	$213.36	$213.35	$213.40
Purchase #2	$127.49	9.523%	$139.6309	$139.63	$139.65	$139.60
Purchase #3	$111.42	13.295%	$126.2333	$126.23	$126.25	$126.20
Purchase #4	$63.59	6.671%	$67.8321	$67.83	$67.85	$67.80
Purchase #5	$183.95	13.186%	$208.2056	$208.21	$208.20	$208.20
Purchase #6	$192.51	9.594%	$210.9794	$210.98	$211.00	$211.00
Purchase #7	$216.89	7.836%	$233.8855	$233.89	$233.90	$233.90
7 purchase totals =	$1,101.78		$1,200.1309	$1,200.13	$1,200.20	$1,200.10