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	$59.32	10.558%	$65.583	$65.58	$65.60	$65.60
Purchase #2	$66.99	8.337%	$72.575	$72.58	$72.60	$72.60
Purchase #3	$224.97	13.299%	$254.8888	$254.89	$254.90	$254.90
Purchase #4	$130.92	6.340%	$139.2203	$139.22	$139.20	$139.20
Purchase #5	$165.98	8.517%	$180.1165	$180.12	$180.10	$180.10
Purchase #6	$153.86	4.126%	$160.2083	$160.21	$160.20	$160.20
Purchase #7	$99.55	4.540%	$104.0696	$104.07	$104.05	$104.10
7 purchase totals =	$901.59		$976.6615	$976.67	$976.65	$976.70