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	$211.32	12.295%	$237.3018	$237.30	$237.30	$237.30
Purchase #2	$193.32	3.695%	$200.4632	$200.46	$200.45	$200.50
Purchase #3	$14.89	4.140%	$15.5064	$15.51	$15.50	$15.50
Purchase #4	$108.39	12.503%	$121.942	$121.94	$121.95	$121.90
Purchase #5	$99.90	5.506%	$105.4005	$105.40	$105.40	$105.40
Purchase #6	$123.82	5.770%	$130.9644	$130.96	$130.95	$131.00
Purchase #7	$128.89	5.540%	$136.0305	$136.03	$136.05	$136.00
7 purchase totals =	$880.53		$947.6088	$947.60	$947.60	$947.60