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	$9.47	13.159%	$10.7162	$10.72	$10.70	$10.70
Purchase #2	$168.50	13.672%	$191.5373	$191.54	$191.55	$191.50
Purchase #3	$49.90	7.693%	$53.7388	$53.74	$53.75	$53.70
Purchase #4	$66.50	13.506%	$75.4815	$75.48	$75.50	$75.50
Purchase #5	$35.78	10.647%	$39.5895	$39.59	$39.60	$39.60
Purchase #6	$148.84	11.529%	$165.9998	$166.00	$166.00	$166.00
Purchase #7	$220.41	9.553%	$241.4658	$241.47	$241.45	$241.50
7 purchase totals =	$699.40		$778.5289	$778.54	$778.55	$778.50