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	$222.30	8.765%	$241.7846	$241.78	$241.80	$241.80
Purchase #2	$91.44	12.361%	$102.7429	$102.74	$102.75	$102.70
Purchase #3	$79.71	13.613%	$90.5609	$90.56	$90.55	$90.60
Purchase #4	$153.60	4.122%	$159.9314	$159.93	$159.95	$159.90
Purchase #5	$167.37	12.549%	$188.3733	$188.37	$188.35	$188.40
Purchase #6	$79.93	4.595%	$83.6028	$83.60	$83.60	$83.60
Purchase #7	$14.66	5.590%	$15.4795	$15.48	$15.50	$15.50
7 purchase totals =	$809.01		$882.4754	$882.46	$882.50	$882.50