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	$14.32	7.754%	$15.4304	$15.43	$15.45	$15.40
Purchase #2	$162.39	10.529%	$179.488	$179.49	$179.50	$179.50
Purchase #3	$24.79	11.581%	$27.6609	$27.66	$27.65	$27.70
Purchase #4	$79.56	4.245%	$82.9373	$82.94	$82.95	$82.90
Purchase #5	$120.61	6.800%	$128.8115	$128.81	$128.80	$128.80
Purchase #6	$46.52	4.229%	$48.4873	$48.49	$48.50	$48.50
Purchase #7	$135.32	6.110%	$143.5881	$143.59	$143.60	$143.60
7 purchase totals =	$583.51		$626.4035	$626.41	$626.45	$626.40