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	$250.27	3.840%	$259.8804	$259.88	$259.90	$259.90
Purchase #2	$33.70	11.638%	$37.622	$37.62	$37.60	$37.60
Purchase #3	$209.66	7.532%	$225.4516	$225.45	$225.45	$225.50
Purchase #4	$60.57	3.792%	$62.8668	$62.87	$62.85	$62.90
Purchase #5	$11.95	13.781%	$13.5968	$13.60	$13.60	$13.60
Purchase #6	$234.48	7.116%	$251.1656	$251.17	$251.15	$251.20
Purchase #7	$204.71	7.393%	$219.8442	$219.84	$219.85	$219.80
7 purchase totals =	$1,005.34		$1,070.4274	$1,070.43	$1,070.40	$1,070.50