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	$72.34	12.652%	$81.4925	$81.49	$81.50	$81.50
Purchase #2	$247.78	4.336%	$258.5237	$258.52	$258.50	$258.50
Purchase #3	$216.25	7.212%	$231.846	$231.85	$231.85	$231.80
Purchase #4	$97.29	4.409%	$101.5795	$101.58	$101.60	$101.60
Purchase #5	$109.32	12.666%	$123.1665	$123.17	$123.15	$123.20
Purchase #6	$153.81	11.211%	$171.0536	$171.05	$171.05	$171.10
Purchase #7	$215.94	10.229%	$238.0285	$238.03	$238.05	$238.00
7 purchase totals =	$1,112.73		$1,205.6903	$1,205.69	$1,205.70	$1,205.70