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	$149.70	7.514%	$160.9485	$160.95	$160.95	$160.90
Purchase #2	$198.90	9.365%	$217.527	$217.53	$217.55	$217.50
Purchase #3	$29.46	10.453%	$32.5395	$32.54	$32.55	$32.50
Purchase #4	$124.85	6.310%	$132.728	$132.73	$132.75	$132.70
Purchase #5	$119.43	10.854%	$132.3929	$132.39	$132.40	$132.40
Purchase #6	$29.73	5.110%	$31.2492	$31.25	$31.25	$31.20
Purchase #7	$179.50	9.268%	$196.1361	$196.14	$196.15	$196.10
7 purchase totals =	$831.57		$903.5212	$903.53	$903.60	$903.30