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	$210.86	5.638%	$222.7483	$222.75	$222.75	$222.70
Purchase #2	$46.86	4.335%	$48.8914	$48.89	$48.90	$48.90
Purchase #3	$187.33	6.103%	$198.7627	$198.76	$198.75	$198.80
Purchase #4	$96.52	7.451%	$103.7117	$103.71	$103.70	$103.70
Purchase #5	$216.55	5.871%	$229.2637	$229.26	$229.25	$229.30
Purchase #6	$62.74	4.125%	$65.328	$65.33	$65.35	$65.30
Purchase #7	$34.51	11.356%	$38.429	$38.43	$38.45	$38.40
7 purchase totals =	$855.37		$907.1348	$907.13	$907.15	$907.10