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	$78.61	10.400%	$86.7854	$86.79	$86.80	$86.80
Purchase #2	$26.70	6.685%	$28.4849	$28.48	$28.50	$28.50
Purchase #3	$73.67	6.490%	$78.4512	$78.45	$78.45	$78.50
Purchase #4	$241.85	10.403%	$267.0097	$267.01	$267.00	$267.00
Purchase #5	$240.43	12.485%	$270.4477	$270.45	$270.45	$270.40
Purchase #6	$11.31	4.621%	$11.8326	$11.83	$11.85	$11.80
Purchase #7	$241.86	4.413%	$252.5333	$252.53	$252.55	$252.50
7 purchase totals =	$914.43		$995.5448	$995.54	$995.60	$995.50