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	$40.85	7.215%	$43.7973	$43.80	$43.80	$43.80
Purchase #2	$117.44	11.250%	$130.652	$130.65	$130.65	$130.70
Purchase #3	$115.57	10.394%	$127.5823	$127.58	$127.60	$127.60
Purchase #4	$31.76	3.149%	$32.7601	$32.76	$32.75	$32.80
Purchase #5	$40.53	10.256%	$44.6868	$44.69	$44.70	$44.70
Purchase #6	$132.55	6.416%	$141.0544	$141.05	$141.05	$141.10
Purchase #7	$196.83	10.774%	$218.0365	$218.04	$218.05	$218.00
7 purchase totals =	$675.53		$738.5694	$738.57	$738.60	$738.70