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	$148.81	10.327%	$164.1776	$164.18	$164.20	$164.20
Purchase #2	$44.39	13.609%	$50.431	$50.43	$50.45	$50.40
Purchase #3	$43.95	13.211%	$49.7562	$49.76	$49.75	$49.80
Purchase #4	$188.92	11.665%	$210.9575	$210.96	$210.95	$211.00
Purchase #5	$164.38	9.237%	$179.5638	$179.56	$179.55	$179.60
Purchase #6	$60.75	3.301%	$62.7554	$62.76	$62.75	$62.80
Purchase #7	$132.56	7.812%	$142.9156	$142.92	$142.90	$142.90
7 purchase totals =	$783.76		$860.5571	$860.57	$860.55	$860.70