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	$102.44	8.687%	$111.339	$111.34	$111.35	$111.30
Purchase #2	$78.41	4.720%	$82.111	$82.11	$82.10	$82.10
Purchase #3	$208.93	11.106%	$232.1338	$232.13	$232.15	$232.10
Purchase #4	$245.87	4.177%	$256.14	$256.14	$256.15	$256.10
Purchase #5	$187.83	10.321%	$207.2159	$207.22	$207.20	$207.20
Purchase #6	$10.88	9.512%	$11.9149	$11.91	$11.90	$11.90
Purchase #7	$153.25	3.363%	$158.4038	$158.40	$158.40	$158.40
7 purchase totals =	$987.61		$1,059.2584	$1,059.25	$1,059.25	$1,059.10