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	$246.35	9.376%	$269.4478	$269.45	$269.45	$269.40
Purchase #2	$61.89	4.622%	$64.7506	$64.75	$64.75	$64.80
Purchase #3	$177.85	10.330%	$196.2219	$196.22	$196.20	$196.20
Purchase #4	$239.54	4.408%	$250.0989	$250.10	$250.10	$250.10
Purchase #5	$92.30	12.758%	$104.0756	$104.08	$104.10	$104.10
Purchase #6	$131.30	7.491%	$141.1357	$141.14	$141.15	$141.10
Purchase #7	$135.91	10.611%	$150.3314	$150.33	$150.35	$150.30
7 purchase totals =	$1,085.14		$1,176.0619	$1,176.07	$1,176.10	$1,176.00