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	$237.58	13.502%	$269.6581	$269.66	$269.65	$269.70
Purchase #2	$48.85	9.850%	$53.6617	$53.66	$53.65	$53.70
Purchase #3	$63.89	12.616%	$71.9504	$71.95	$71.95	$72.00
Purchase #4	$145.80	9.243%	$159.2763	$159.28	$159.30	$159.30
Purchase #5	$38.28	6.126%	$40.625	$40.63	$40.65	$40.60
Purchase #6	$148.49	12.146%	$166.5256	$166.53	$166.55	$166.50
Purchase #7	$242.96	5.181%	$255.5478	$255.55	$255.55	$255.50
7 purchase totals =	$925.85		$1,017.2449	$1,017.26	$1,017.30	$1,017.30