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	$43.50	4.272%	$45.3583	$45.36	$45.35	$45.40
Purchase #2	$139.70	3.500%	$144.5895	$144.59	$144.60	$144.60
Purchase #3	$121.63	9.629%	$133.3418	$133.34	$133.35	$133.30
Purchase #4	$234.61	11.871%	$262.4606	$262.46	$262.45	$262.50
Purchase #5	$146.89	6.681%	$156.7037	$156.70	$156.70	$156.70
Purchase #6	$76.47	6.491%	$81.4337	$81.43	$81.45	$81.40
Purchase #7	$195.79	13.430%	$222.0846	$222.08	$222.10	$222.10
7 purchase totals =	$958.59		$1,045.9722	$1,045.96	$1,046.00	$1,046.00