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	$59.83	9.788%	$65.6862	$65.69	$65.70	$65.70
Purchase #2	$186.86	7.133%	$200.1887	$200.19	$200.20	$200.20
Purchase #3	$208.28	4.153%	$216.9299	$216.93	$216.95	$216.90
Purchase #4	$189.95	4.164%	$197.8595	$197.86	$197.85	$197.90
Purchase #5	$239.66	13.773%	$272.6684	$272.67	$272.65	$272.70
Purchase #6	$43.85	4.709%	$45.9149	$45.91	$45.90	$45.90
Purchase #7	$93.82	8.324%	$101.6296	$101.63	$101.65	$101.60
7 purchase totals =	$1,022.25		$1,100.8772	$1,100.88	$1,100.90	$1,100.90