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	$244.55	7.424%	$262.7054	$262.71	$262.70	$262.70
Purchase #2	$98.30	13.497%	$111.5676	$111.57	$111.55	$111.60
Purchase #3	$138.66	11.593%	$154.7349	$154.73	$154.75	$154.70
Purchase #4	$217.52	6.540%	$231.7458	$231.75	$231.75	$231.70
Purchase #5	$112.94	9.324%	$123.4705	$123.47	$123.45	$123.50
Purchase #6	$109.79	12.383%	$123.3853	$123.39	$123.40	$123.40
Purchase #7	$211.54	7.142%	$226.6482	$226.65	$226.65	$226.60
7 purchase totals =	$1,133.30		$1,234.2577	$1,234.27	$1,234.25	$1,234.20