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	$136.92	4.830%	$143.5332	$143.53	$143.55	$143.50
Purchase #2	$89.88	7.502%	$96.6228	$96.62	$96.60	$96.60
Purchase #3	$18.54	4.536%	$19.381	$19.38	$19.40	$19.40
Purchase #4	$248.35	3.274%	$256.481	$256.48	$256.50	$256.50
Purchase #5	$61.40	8.115%	$66.3826	$66.38	$66.40	$66.40
Purchase #6	$115.98	12.480%	$130.4543	$130.45	$130.45	$130.50
Purchase #7	$13.40	10.240%	$14.7722	$14.77	$14.75	$14.80
7 purchase totals =	$684.47		$727.6271	$727.61	$727.65	$727.70