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	$16.31	6.660%	$17.3962	$17.40	$17.40	$17.40
Purchase #2	$31.31	13.211%	$35.4464	$35.45	$35.45	$35.40
Purchase #3	$111.69	4.702%	$116.9417	$116.94	$116.95	$116.90
Purchase #4	$64.25	4.321%	$67.0262	$67.03	$67.05	$67.00
Purchase #5	$119.95	9.600%	$131.4652	$131.47	$131.45	$131.50
Purchase #6	$225.80	6.830%	$241.2221	$241.22	$241.20	$241.20
Purchase #7	$98.55	6.457%	$104.9134	$104.91	$104.90	$104.90
7 purchase totals =	$667.86		$714.4112	$714.42	$714.40	$714.30