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	$72.95	7.633%	$78.5183	$78.52	$78.50	$78.50
Purchase #2	$70.40	9.412%	$77.026	$77.03	$77.05	$77.00
Purchase #3	$169.90	5.584%	$179.3872	$179.39	$179.40	$179.40
Purchase #4	$166.73	7.600%	$179.4015	$179.40	$179.40	$179.40
Purchase #5	$172.89	7.341%	$185.5819	$185.58	$185.60	$185.60
Purchase #6	$13.68	8.112%	$14.7897	$14.79	$14.80	$14.80
Purchase #7	$42.50	10.168%	$46.8214	$46.82	$46.80	$46.80
7 purchase totals =	$709.05		$761.5260	$761.53	$761.55	$761.50