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	$67.61	4.410%	$70.5916	$70.59	$70.60	$70.60
Purchase #2	$159.75	5.438%	$168.4372	$168.44	$168.45	$168.40
Purchase #3	$58.52	11.127%	$65.0315	$65.03	$65.05	$65.00
Purchase #4	$49.64	12.700%	$55.9443	$55.94	$55.95	$55.90
Purchase #5	$40.52	3.510%	$41.9423	$41.94	$41.95	$41.90
Purchase #6	$133.69	13.126%	$151.2381	$151.24	$151.25	$151.20
Purchase #7	$186.54	5.450%	$196.7064	$196.71	$196.70	$196.70
7 purchase totals =	$696.27		$749.8914	$749.89	$749.95	$749.70