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	$199.46	5.652%	$210.7335	$210.73	$210.75	$210.70
Purchase #2	$112.59	9.501%	$123.2872	$123.29	$123.30	$123.30
Purchase #3	$105.93	10.253%	$116.791	$116.79	$116.80	$116.80
Purchase #4	$200.33	10.767%	$221.8995	$221.90	$221.90	$221.90
Purchase #5	$55.81	6.137%	$59.2351	$59.24	$59.25	$59.20
Purchase #6	$54.69	11.197%	$60.8136	$60.81	$60.80	$60.80
Purchase #7	$183.90	11.852%	$205.6958	$205.70	$205.70	$205.70
7 purchase totals =	$912.71		$998.4557	$998.46	$998.50	$998.40