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	$164.58	8.511%	$178.5874	$178.59	$178.60	$178.60
Purchase #2	$181.93	5.396%	$191.7469	$191.75	$191.75	$191.70
Purchase #3	$158.67	5.110%	$166.778	$166.78	$166.80	$166.80
Purchase #4	$15.80	11.358%	$17.5946	$17.59	$17.60	$17.60
Purchase #5	$53.26	11.734%	$59.5095	$59.51	$59.50	$59.50
Purchase #6	$17.85	11.469%	$19.8972	$19.90	$19.90	$19.90
Purchase #7	$30.43	11.122%	$33.8144	$33.81	$33.80	$33.80
7 purchase totals =	$622.52		$667.9280	$667.93	$667.95	$667.90