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	$210.65	13.364%	$238.8013	$238.80	$238.80	$238.80
Purchase #2	$183.63	13.396%	$208.2291	$208.23	$208.25	$208.20
Purchase #3	$47.99	6.610%	$51.1621	$51.16	$51.15	$51.20
Purchase #4	$147.87	5.328%	$155.7485	$155.75	$155.75	$155.70
Purchase #5	$34.47	9.738%	$37.8267	$37.83	$37.85	$37.80
Purchase #6	$243.81	7.646%	$262.4517	$262.45	$262.45	$262.50
Purchase #7	$112.31	9.757%	$123.2681	$123.27	$123.25	$123.30
7 purchase totals =	$980.73		$1,077.4875	$1,077.49	$1,077.50	$1,077.50