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	$111.86	13.806%	$127.3034	$127.30	$127.30	$127.30
Purchase #2	$72.53	8.850%	$78.9489	$78.95	$78.95	$78.90
Purchase #3	$105.58	5.662%	$111.5579	$111.56	$111.55	$111.60
Purchase #4	$178.32	11.583%	$198.9748	$198.97	$198.95	$199.00
Purchase #5	$165.60	9.492%	$181.3188	$181.32	$181.30	$181.30
Purchase #6	$69.54	9.498%	$76.1449	$76.14	$76.15	$76.10
Purchase #7	$106.56	9.295%	$116.4648	$116.46	$116.45	$116.50
7 purchase totals =	$809.99		$890.7135	$890.70	$890.65	$890.70