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	$129.40	11.719%	$144.5644	$144.56	$144.55	$144.60
Purchase #2	$185.67	13.396%	$210.5424	$210.54	$210.55	$210.50
Purchase #3	$54.50	7.844%	$58.775	$58.78	$58.80	$58.80
Purchase #4	$158.51	10.162%	$174.6178	$174.62	$174.60	$174.60
Purchase #5	$195.87	6.351%	$208.3097	$208.31	$208.30	$208.30
Purchase #6	$174.38	6.386%	$185.5159	$185.52	$185.50	$185.50
Purchase #7	$242.46	5.605%	$256.0499	$256.05	$256.05	$256.00
7 purchase totals =	$1,140.79		$1,238.3751	$1,238.38	$1,238.35	$1,238.30