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	$205.69	12.381%	$231.1565	$231.16	$231.15	$231.20
Purchase #2	$180.31	12.632%	$203.0868	$203.09	$203.10	$203.10
Purchase #3	$214.45	8.862%	$233.4546	$233.45	$233.45	$233.50
Purchase #4	$88.72	10.712%	$98.2237	$98.22	$98.20	$98.20
Purchase #5	$204.27	8.261%	$221.1447	$221.14	$221.15	$221.10
Purchase #6	$95.83	13.529%	$108.7948	$108.79	$108.80	$108.80
Purchase #7	$86.29	4.256%	$89.9625	$89.96	$89.95	$90.00
7 purchase totals =	$1,075.56		$1,185.8236	$1,185.81	$1,185.80	$1,185.90