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	$133.44	6.314%	$141.8654	$141.87	$141.85	$141.90
Purchase #2	$55.31	4.150%	$57.6054	$57.61	$57.60	$57.60
Purchase #3	$121.58	9.279%	$132.8614	$132.86	$132.85	$132.90
Purchase #4	$101.87	12.823%	$114.9328	$114.93	$114.95	$114.90
Purchase #5	$146.65	8.292%	$158.8102	$158.81	$158.80	$158.80
Purchase #6	$181.59	4.669%	$190.0684	$190.07	$190.05	$190.10
Purchase #7	$219.51	12.132%	$246.141	$246.14	$246.15	$246.10
7 purchase totals =	$959.95		$1,042.2846	$1,042.29	$1,042.25	$1,042.30