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	$151.94	13.618%	$172.6312	$172.63	$172.65	$172.60
Purchase #2	$126.81	3.223%	$130.8971	$130.90	$130.90	$130.90
Purchase #3	$127.61	5.305%	$134.3797	$134.38	$134.40	$134.40
Purchase #4	$200.47	7.786%	$216.0786	$216.08	$216.10	$216.10
Purchase #5	$11.94	12.727%	$13.4596	$13.46	$13.45	$13.50
Purchase #6	$194.28	12.793%	$219.1342	$219.13	$219.15	$219.10
Purchase #7	$229.32	4.666%	$240.0201	$240.02	$240.00	$240.00
7 purchase totals =	$1,042.37		$1,126.6005	$1,126.60	$1,126.65	$1,126.60