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	$109.86	5.696%	$116.1176	$116.12	$116.10	$116.10
Purchase #2	$10.85	9.323%	$11.8615	$11.86	$11.85	$11.90
Purchase #3	$49.63	12.514%	$55.8407	$55.84	$55.85	$55.80
Purchase #4	$88.31	13.615%	$100.3334	$100.33	$100.35	$100.30
Purchase #5	$227.60	13.291%	$257.8503	$257.85	$257.85	$257.90
Purchase #6	$61.37	4.760%	$64.2912	$64.29	$64.30	$64.30
Purchase #7	$9.68	13.114%	$10.9494	$10.95	$10.95	$10.90
7 purchase totals =	$557.30		$617.2441	$617.24	$617.25	$617.20