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	$217.36	6.811%	$232.1644	$232.16	$232.15	$232.20
Purchase #2	$89.26	12.327%	$100.2631	$100.26	$100.25	$100.30
Purchase #3	$215.54	3.789%	$223.7068	$223.71	$223.70	$223.70
Purchase #4	$158.94	12.361%	$178.5866	$178.59	$178.60	$178.60
Purchase #5	$164.68	3.546%	$170.5196	$170.52	$170.50	$170.50
Purchase #6	$54.91	13.140%	$62.1252	$62.13	$62.15	$62.10
Purchase #7	$249.31	4.357%	$260.1724	$260.17	$260.15	$260.20
7 purchase totals =	$1,150.00		$1,227.5381	$1,227.54	$1,227.50	$1,227.60