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	$243.51	13.720%	$276.9196	$276.92	$276.90	$276.90
Purchase #2	$45.64	3.681%	$47.32	$47.32	$47.30	$47.30
Purchase #3	$209.55	7.237%	$224.7151	$224.72	$224.70	$224.70
Purchase #4	$169.64	10.189%	$186.9246	$186.92	$186.90	$186.90
Purchase #5	$126.95	9.408%	$138.8935	$138.89	$138.90	$138.90
Purchase #6	$111.80	10.505%	$123.5446	$123.54	$123.55	$123.50
Purchase #7	$52.31	7.705%	$56.3405	$56.34	$56.35	$56.30
7 purchase totals =	$959.40		$1,054.6579	$1,054.65	$1,054.60	$1,054.50