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	$133.26	11.399%	$148.4503	$148.45	$148.45	$148.50
Purchase #2	$64.47	8.232%	$69.7772	$69.78	$69.80	$69.80
Purchase #3	$72.72	8.602%	$78.9754	$78.98	$79.00	$79.00
Purchase #4	$180.61	8.779%	$196.4658	$196.47	$196.45	$196.50
Purchase #5	$154.82	11.650%	$172.8565	$172.86	$172.85	$172.90
Purchase #6	$120.82	5.724%	$127.7357	$127.74	$127.75	$127.70
Purchase #7	$236.28	5.262%	$248.7131	$248.71	$248.70	$248.70
7 purchase totals =	$962.98		$1,042.9740	$1,042.99	$1,043.00	$1,043.10