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	$223.74	4.329%	$233.4257	$233.43	$233.45	$233.40
Purchase #2	$169.99	6.134%	$180.4172	$180.42	$180.40	$180.40
Purchase #3	$36.71	9.438%	$40.1747	$40.17	$40.15	$40.20
Purchase #4	$128.65	9.631%	$141.0403	$141.04	$141.05	$141.00
Purchase #5	$49.29	11.131%	$54.7765	$54.78	$54.80	$54.80
Purchase #6	$214.69	7.223%	$230.1971	$230.20	$230.20	$230.20
Purchase #7	$91.47	4.353%	$95.4517	$95.45	$95.45	$95.50
7 purchase totals =	$914.54		$975.4832	$975.49	$975.50	$975.50