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	$117.81	13.424%	$133.6248	$133.62	$133.60	$133.60
Purchase #2	$234.42	13.159%	$265.2673	$265.27	$265.25	$265.30
Purchase #3	$151.97	7.344%	$163.1307	$163.13	$163.15	$163.10
Purchase #4	$50.38	11.129%	$55.9868	$55.99	$56.00	$56.00
Purchase #5	$90.77	11.213%	$100.948	$100.95	$100.95	$100.90
Purchase #6	$114.55	11.326%	$127.5239	$127.52	$127.50	$127.50
Purchase #7	$234.90	5.816%	$248.5618	$248.56	$248.55	$248.60
7 purchase totals =	$994.80		$1,095.0433	$1,095.04	$1,095.00	$1,095.00