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	$126.66	4.151%	$131.9177	$131.92	$131.90	$131.90
Purchase #2	$62.71	6.237%	$66.6212	$66.62	$66.60	$66.60
Purchase #3	$31.55	5.764%	$33.3685	$33.37	$33.35	$33.40
Purchase #4	$79.81	10.325%	$88.0504	$88.05	$88.05	$88.10
Purchase #5	$201.54	7.138%	$215.9259	$215.93	$215.95	$215.90
Purchase #6	$108.83	8.847%	$118.4582	$118.46	$118.45	$118.50
Purchase #7	$150.62	3.220%	$155.47	$155.47	$155.45	$155.50
7 purchase totals =	$761.72		$809.8119	$809.82	$809.75	$809.90