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	$9.97	7.577%	$10.7254	$10.73	$10.75	$10.70
Purchase #2	$191.54	13.476%	$217.3519	$217.35	$217.35	$217.40
Purchase #3	$214.52	12.624%	$241.601	$241.60	$241.60	$241.60
Purchase #4	$10.29	8.432%	$11.1577	$11.16	$11.15	$11.20
Purchase #5	$38.89	10.459%	$42.9575	$42.96	$42.95	$43.00
Purchase #6	$188.88	10.380%	$208.4857	$208.49	$208.50	$208.50
Purchase #7	$27.42	13.330%	$31.0751	$31.08	$31.10	$31.10
7 purchase totals =	$681.51		$763.3543	$763.37	$763.40	$763.50