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	$43.47	5.646%	$45.9243	$45.92	$45.90	$45.90
Purchase #2	$154.27	5.756%	$163.1498	$163.15	$163.15	$163.10
Purchase #3	$192.86	13.483%	$218.8633	$218.86	$218.85	$218.90
Purchase #4	$49.28	12.701%	$55.5391	$55.54	$55.55	$55.50
Purchase #5	$10.69	6.497%	$11.3845	$11.38	$11.40	$11.40
Purchase #6	$142.90	13.707%	$162.4873	$162.49	$162.50	$162.50
Purchase #7	$167.78	13.609%	$190.6132	$190.61	$190.60	$190.60
7 purchase totals =	$761.25		$847.9615	$847.95	$847.95	$847.90