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	$155.40	4.751%	$162.7831	$162.78	$162.80	$162.80
Purchase #2	$43.48	10.836%	$48.1915	$48.19	$48.20	$48.20
Purchase #3	$229.59	9.193%	$250.6962	$250.70	$250.70	$250.70
Purchase #4	$181.47	12.786%	$204.6728	$204.67	$204.65	$204.70
Purchase #5	$162.50	11.629%	$181.3971	$181.40	$181.40	$181.40
Purchase #6	$98.29	13.363%	$111.4245	$111.42	$111.40	$111.40
Purchase #7	$106.98	9.487%	$117.1292	$117.13	$117.15	$117.10
7 purchase totals =	$977.71		$1,076.2944	$1,076.29	$1,076.30	$1,076.30