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	$215.53	3.538%	$223.1555	$223.16	$223.15	$223.20
Purchase #2	$52.90	12.307%	$59.4104	$59.41	$59.40	$59.40
Purchase #3	$132.75	5.751%	$140.3845	$140.38	$140.40	$140.40
Purchase #4	$188.99	4.476%	$197.4492	$197.45	$197.45	$197.40
Purchase #5	$48.74	8.454%	$52.8605	$52.86	$52.85	$52.90
Purchase #6	$100.55	3.366%	$103.9345	$103.93	$103.95	$103.90
Purchase #7	$160.82	7.773%	$173.3205	$173.32	$173.30	$173.30
7 purchase totals =	$900.28		$950.5151	$950.51	$950.50	$950.50