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	$176.75	3.761%	$183.3976	$183.40	$183.40	$183.40
Purchase #2	$163.58	11.584%	$182.5291	$182.53	$182.55	$182.50
Purchase #3	$189.43	12.701%	$213.4895	$213.49	$213.50	$213.50
Purchase #4	$203.97	3.767%	$211.6535	$211.65	$211.65	$211.70
Purchase #5	$246.31	10.149%	$271.308	$271.31	$271.30	$271.30
Purchase #6	$153.83	12.801%	$173.5218	$173.52	$173.50	$173.50
Purchase #7	$74.72	4.754%	$78.2722	$78.27	$78.25	$78.30
7 purchase totals =	$1,208.59		$1,314.1717	$1,314.17	$1,314.15	$1,314.20