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	$23.76	11.385%	$26.4651	$26.47	$26.45	$26.50
Purchase #2	$162.34	10.152%	$178.8208	$178.82	$178.80	$178.80
Purchase #3	$109.40	12.643%	$123.2314	$123.23	$123.25	$123.20
Purchase #4	$171.36	9.584%	$187.7831	$187.78	$187.80	$187.80
Purchase #5	$186.66	7.397%	$200.4672	$200.47	$200.45	$200.50
Purchase #6	$167.30	5.400%	$176.3342	$176.33	$176.35	$176.30
Purchase #7	$130.43	10.558%	$144.2008	$144.20	$144.20	$144.20
7 purchase totals =	$951.25		$1,037.3026	$1,037.30	$1,037.30	$1,037.30