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	$227.71	13.585%	$258.6444	$258.64	$258.65	$258.60
Purchase #2	$99.97	3.536%	$103.5049	$103.50	$103.50	$103.50
Purchase #3	$184.81	13.865%	$210.4339	$210.43	$210.45	$210.40
Purchase #4	$49.40	3.318%	$51.0391	$51.04	$51.05	$51.00
Purchase #5	$140.29	10.856%	$155.5199	$155.52	$155.50	$155.50
Purchase #6	$73.54	6.435%	$78.2723	$78.27	$78.25	$78.30
Purchase #7	$207.69	7.762%	$223.8109	$223.81	$223.80	$223.80
7 purchase totals =	$983.41		$1,081.2254	$1,081.21	$1,081.20	$1,081.10