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	$160.54	6.516%	$171.0008	$171.00	$171.00	$171.00
Purchase #2	$136.95	5.429%	$144.385	$144.39	$144.40	$144.40
Purchase #3	$43.52	3.108%	$44.8726	$44.87	$44.85	$44.90
Purchase #4	$168.89	8.404%	$183.0835	$183.08	$183.10	$183.10
Purchase #5	$196.72	9.298%	$215.011	$215.01	$215.00	$215.00
Purchase #6	$121.63	8.687%	$132.196	$132.20	$132.20	$132.20
Purchase #7	$181.98	7.113%	$194.9242	$194.92	$194.90	$194.90
7 purchase totals =	$1,010.23		$1,085.4731	$1,085.47	$1,085.45	$1,085.50