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	$182.90	10.778%	$202.613	$202.61	$202.60	$202.60
Purchase #2	$123.59	6.759%	$131.9434	$131.94	$131.95	$131.90
Purchase #3	$121.54	4.728%	$127.2864	$127.29	$127.30	$127.30
Purchase #4	$37.78	4.307%	$39.4072	$39.41	$39.40	$39.40
Purchase #5	$155.99	5.528%	$164.6131	$164.61	$164.60	$164.60
Purchase #6	$87.68	11.250%	$97.544	$97.54	$97.55	$97.50
Purchase #7	$238.99	9.178%	$260.9245	$260.92	$260.90	$260.90
7 purchase totals =	$948.47		$1,024.3316	$1,024.32	$1,024.30	$1,024.20