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	$132.41	8.451%	$143.6	$143.60	$143.60	$143.60
Purchase #2	$51.79	6.362%	$55.0849	$55.08	$55.10	$55.10
Purchase #3	$102.79	13.783%	$116.9575	$116.96	$116.95	$117.00
Purchase #4	$200.50	5.761%	$212.0508	$212.05	$212.05	$212.10
Purchase #5	$30.25	6.792%	$32.3046	$32.30	$32.30	$32.30
Purchase #6	$82.66	8.185%	$89.4257	$89.43	$89.45	$89.40
Purchase #7	$59.43	3.267%	$61.3716	$61.37	$61.35	$61.40
7 purchase totals =	$659.83		$710.7951	$710.79	$710.80	$710.90