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	$164.51	4.847%	$172.4838	$172.48	$172.50	$172.50
Purchase #2	$239.27	12.495%	$269.1668	$269.17	$269.15	$269.20
Purchase #3	$50.60	8.859%	$55.0827	$55.08	$55.10	$55.10
Purchase #4	$11.39	3.724%	$11.8142	$11.81	$11.80	$11.80
Purchase #5	$233.37	7.349%	$250.5204	$250.52	$250.50	$250.50
Purchase #6	$215.78	4.489%	$225.4664	$225.47	$225.45	$225.50
Purchase #7	$216.39	3.483%	$223.9269	$223.93	$223.95	$223.90
7 purchase totals =	$1,131.31		$1,208.4612	$1,208.46	$1,208.45	$1,208.50