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	$9.32	10.489%	$10.2976	$10.30	$10.30	$10.30
Purchase #2	$13.31	8.594%	$14.4539	$14.45	$14.45	$14.50
Purchase #3	$83.98	4.442%	$87.7104	$87.71	$87.70	$87.70
Purchase #4	$50.72	9.322%	$55.4481	$55.45	$55.45	$55.40
Purchase #5	$59.51	8.593%	$64.6237	$64.62	$64.60	$64.60
Purchase #6	$134.32	5.342%	$141.4954	$141.50	$141.50	$141.50
Purchase #7	$109.43	6.772%	$116.8406	$116.84	$116.85	$116.80
7 purchase totals =	$460.59		$490.8697	$490.87	$490.85	$490.80