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	$244.77	8.553%	$265.7052	$265.71	$265.70	$265.70
Purchase #2	$35.90	12.254%	$40.2992	$40.30	$40.30	$40.30
Purchase #3	$189.75	5.857%	$200.8637	$200.86	$200.85	$200.90
Purchase #4	$85.60	5.746%	$90.5186	$90.52	$90.50	$90.50
Purchase #5	$86.75	6.661%	$92.5284	$92.53	$92.55	$92.50
Purchase #6	$115.73	3.306%	$119.556	$119.56	$119.55	$119.60
Purchase #7	$230.38	13.669%	$261.8706	$261.87	$261.85	$261.90
7 purchase totals =	$988.88		$1,071.3417	$1,071.35	$1,071.30	$1,071.40