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	$200.76	11.265%	$223.3756	$223.38	$223.40	$223.40
Purchase #2	$129.77	9.105%	$141.5856	$141.59	$141.60	$141.60
Purchase #3	$232.88	12.122%	$261.1097	$261.11	$261.10	$261.10
Purchase #4	$204.50	13.243%	$231.5819	$231.58	$231.60	$231.60
Purchase #5	$96.93	13.398%	$109.9167	$109.92	$109.90	$109.90
Purchase #6	$32.35	5.130%	$34.0096	$34.01	$34.00	$34.00
Purchase #7	$158.76	12.677%	$178.886	$178.89	$178.90	$178.90
7 purchase totals =	$1,055.95		$1,180.4651	$1,180.48	$1,180.50	$1,180.50