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	$29.62	8.728%	$32.2052	$32.21	$32.20	$32.20
Purchase #2	$59.79	5.791%	$63.2524	$63.25	$63.25	$63.30
Purchase #3	$96.75	6.606%	$103.1413	$103.14	$103.15	$103.10
Purchase #4	$230.61	10.105%	$253.9131	$253.91	$253.90	$253.90
Purchase #5	$65.86	10.480%	$72.7621	$72.76	$72.75	$72.80
Purchase #6	$192.57	4.344%	$200.9352	$200.94	$200.95	$200.90
Purchase #7	$50.96	10.455%	$56.2879	$56.29	$56.30	$56.30
7 purchase totals =	$726.16		$782.4972	$782.50	$782.50	$782.50