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	$224.40	4.507%	$234.5137	$234.51	$234.50	$234.50
Purchase #2	$12.37	8.333%	$13.4008	$13.40	$13.40	$13.40
Purchase #3	$70.86	9.304%	$77.4528	$77.45	$77.45	$77.50
Purchase #4	$250.66	9.483%	$274.4301	$274.43	$274.45	$274.40
Purchase #5	$238.72	3.108%	$246.1394	$246.14	$246.15	$246.10
Purchase #6	$234.26	10.418%	$258.6652	$258.67	$258.65	$258.70
Purchase #7	$183.84	6.874%	$196.4772	$196.48	$196.50	$196.50
7 purchase totals =	$1,215.11		$1,301.0792	$1,301.08	$1,301.10	$1,301.10