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	$106.96	9.141%	$116.7372	$116.74	$116.75	$116.70
Purchase #2	$211.67	5.602%	$223.5278	$223.53	$223.55	$223.50
Purchase #3	$137.72	11.490%	$153.544	$153.54	$153.55	$153.50
Purchase #4	$238.81	13.273%	$270.5073	$270.51	$270.50	$270.50
Purchase #5	$72.57	6.170%	$77.0476	$77.05	$77.05	$77.00
Purchase #6	$127.82	3.724%	$132.58	$132.58	$132.60	$132.60
Purchase #7	$161.43	4.264%	$168.3134	$168.31	$168.30	$168.30
7 purchase totals =	$1,056.98		$1,142.2573	$1,142.26	$1,142.30	$1,142.10