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	$167.99	5.285%	$176.8683	$176.87	$176.85	$176.90
Purchase #2	$164.28	10.136%	$180.9314	$180.93	$180.95	$180.90
Purchase #3	$213.77	10.592%	$236.4125	$236.41	$236.40	$236.40
Purchase #4	$70.92	10.687%	$78.4992	$78.50	$78.50	$78.50
Purchase #5	$230.88	11.618%	$257.7036	$257.70	$257.70	$257.70
Purchase #6	$143.46	10.577%	$158.6338	$158.63	$158.65	$158.60
Purchase #7	$54.88	11.711%	$61.307	$61.31	$61.30	$61.30
7 purchase totals =	$1,046.18		$1,150.3558	$1,150.35	$1,150.35	$1,150.30