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	$48.77	5.773%	$51.5855	$51.59	$51.60	$51.60
Purchase #2	$229.48	11.788%	$256.5311	$256.53	$256.55	$256.50
Purchase #3	$199.63	5.480%	$210.5697	$210.57	$210.55	$210.60
Purchase #4	$32.89	9.803%	$36.1142	$36.11	$36.10	$36.10
Purchase #5	$246.72	4.321%	$257.3808	$257.38	$257.40	$257.40
Purchase #6	$106.46	13.261%	$120.5777	$120.58	$120.60	$120.60
Purchase #7	$79.70	3.196%	$82.2472	$82.25	$82.25	$82.20
7 purchase totals =	$943.65		$1,015.0062	$1,015.01	$1,015.05	$1,015.00