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	$232.25	11.749%	$259.5371	$259.54	$259.55	$259.50
Purchase #2	$77.81	6.119%	$82.5712	$82.57	$82.55	$82.60
Purchase #3	$200.80	7.866%	$216.5949	$216.59	$216.60	$216.60
Purchase #4	$222.93	4.796%	$233.6217	$233.62	$233.60	$233.60
Purchase #5	$126.73	11.247%	$140.9833	$140.98	$141.00	$141.00
Purchase #6	$187.53	12.721%	$211.3857	$211.39	$211.40	$211.40
Purchase #7	$36.83	7.116%	$39.4508	$39.45	$39.45	$39.50
7 purchase totals =	$1,084.88		$1,184.1447	$1,184.14	$1,184.15	$1,184.20