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	$133.52	10.366%	$147.3607	$147.36	$147.35	$147.40
Purchase #2	$217.51	4.766%	$227.8765	$227.88	$227.90	$227.90
Purchase #3	$228.96	9.378%	$250.4319	$250.43	$250.45	$250.40
Purchase #4	$194.28	3.407%	$200.8991	$200.90	$200.90	$200.90
Purchase #5	$15.57	5.803%	$16.4735	$16.47	$16.45	$16.50
Purchase #6	$139.57	13.536%	$158.4622	$158.46	$158.45	$158.50
Purchase #7	$60.93	10.605%	$67.3916	$67.39	$67.40	$67.40
7 purchase totals =	$990.34		$1,068.8955	$1,068.89	$1,068.90	$1,069.00