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	$154.96	5.394%	$163.3185	$163.32	$163.30	$163.30
Purchase #2	$88.38	13.830%	$100.603	$100.60	$100.60	$100.60
Purchase #3	$135.72	4.633%	$142.0079	$142.01	$142.00	$142.00
Purchase #4	$243.51	13.731%	$276.9464	$276.95	$276.95	$276.90
Purchase #5	$42.64	8.110%	$46.0981	$46.10	$46.10	$46.10
Purchase #6	$34.39	11.446%	$38.3263	$38.33	$38.35	$38.30
Purchase #7	$38.47	4.705%	$40.28	$40.28	$40.30	$40.30
7 purchase totals =	$738.07		$807.5802	$807.59	$807.60	$807.50