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	$218.95	13.663%	$248.8651	$248.87	$248.85	$248.90
Purchase #2	$18.45	3.718%	$19.136	$19.14	$19.15	$19.10
Purchase #3	$179.86	11.557%	$200.6464	$200.65	$200.65	$200.60
Purchase #4	$53.31	10.806%	$59.0707	$59.07	$59.05	$59.10
Purchase #5	$21.40	9.576%	$23.4493	$23.45	$23.45	$23.40
Purchase #6	$11.88	7.466%	$12.767	$12.77	$12.75	$12.80
Purchase #7	$188.75	13.158%	$213.5857	$213.59	$213.60	$213.60
7 purchase totals =	$692.60		$777.5202	$777.54	$777.50	$777.50