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	$67.77	7.230%	$72.6698	$72.67	$72.65	$72.70
Purchase #2	$99.54	6.405%	$105.9155	$105.92	$105.90	$105.90
Purchase #3	$115.63	9.769%	$126.9259	$126.93	$126.95	$126.90
Purchase #4	$63.84	4.342%	$66.6119	$66.61	$66.60	$66.60
Purchase #5	$176.93	7.313%	$189.8689	$189.87	$189.85	$189.90
Purchase #6	$101.95	5.240%	$107.2922	$107.29	$107.30	$107.30
Purchase #7	$72.70	13.134%	$82.2484	$82.25	$82.25	$82.20
7 purchase totals =	$698.36		$751.5326	$751.54	$751.50	$751.50