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	$183.89	4.641%	$192.4243	$192.42	$192.40	$192.40
Purchase #2	$163.61	3.851%	$169.9106	$169.91	$169.90	$169.90
Purchase #3	$43.81	11.749%	$48.9572	$48.96	$48.95	$49.00
Purchase #4	$108.52	13.813%	$123.5099	$123.51	$123.50	$123.50
Purchase #5	$31.54	4.871%	$33.0763	$33.08	$33.10	$33.10
Purchase #6	$12.43	8.296%	$13.4612	$13.46	$13.45	$13.50
Purchase #7	$160.73	13.491%	$182.4141	$182.41	$182.40	$182.40
7 purchase totals =	$704.53		$763.7536	$763.75	$763.70	$763.80