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	$102.31	9.833%	$112.3701	$112.37	$112.35	$112.40
Purchase #2	$242.49	5.843%	$256.6587	$256.66	$256.65	$256.70
Purchase #3	$42.89	8.402%	$46.4936	$46.49	$46.50	$46.50
Purchase #4	$172.57	12.576%	$194.2724	$194.27	$194.25	$194.30
Purchase #5	$55.52	3.808%	$57.6342	$57.63	$57.65	$57.60
Purchase #6	$231.37	5.282%	$243.591	$243.59	$243.60	$243.60
Purchase #7	$183.89	6.687%	$196.1867	$196.19	$196.20	$196.20
7 purchase totals =	$1,031.04		$1,107.2067	$1,107.20	$1,107.20	$1,107.30