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	$204.27	5.435%	$215.3721	$215.37	$215.35	$215.40
Purchase #2	$53.54	8.708%	$58.2023	$58.20	$58.20	$58.20
Purchase #3	$78.45	5.283%	$82.5945	$82.59	$82.60	$82.60
Purchase #4	$239.62	9.683%	$262.8224	$262.82	$262.80	$262.80
Purchase #5	$93.65	7.658%	$100.8217	$100.82	$100.80	$100.80
Purchase #6	$104.62	6.754%	$111.686	$111.69	$111.70	$111.70
Purchase #7	$185.58	11.730%	$207.3485	$207.35	$207.35	$207.30
7 purchase totals =	$959.73		$1,038.8475	$1,038.84	$1,038.80	$1,038.80