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	$164.26	7.331%	$176.3019	$176.30	$176.30	$176.30
Purchase #2	$36.80	10.138%	$40.5308	$40.53	$40.55	$40.50
Purchase #3	$61.84	13.245%	$70.0307	$70.03	$70.05	$70.00
Purchase #4	$178.43	11.357%	$198.6943	$198.69	$198.70	$198.70
Purchase #5	$106.52	4.673%	$111.4977	$111.50	$111.50	$111.50
Purchase #6	$95.30	4.699%	$99.7781	$99.78	$99.80	$99.80
Purchase #7	$183.69	3.767%	$190.6096	$190.61	$190.60	$190.60
7 purchase totals =	$826.84		$887.4431	$887.44	$887.50	$887.40