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	$64.66	4.153%	$67.3453	$67.35	$67.35	$67.30
Purchase #2	$69.75	3.862%	$72.4437	$72.44	$72.45	$72.40
Purchase #3	$209.72	9.728%	$230.1216	$230.12	$230.10	$230.10
Purchase #4	$71.89	4.525%	$75.143	$75.14	$75.15	$75.10
Purchase #5	$50.45	3.363%	$52.1466	$52.15	$52.15	$52.10
Purchase #6	$224.36	5.856%	$237.4985	$237.50	$237.50	$237.50
Purchase #7	$163.81	5.289%	$172.4739	$172.47	$172.45	$172.50
7 purchase totals =	$854.64		$907.1726	$907.17	$907.15	$907.00