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	$127.52	7.758%	$137.413	$137.41	$137.40	$137.40
Purchase #2	$132.60	6.527%	$141.2548	$141.25	$141.25	$141.30
Purchase #3	$242.48	6.683%	$258.6849	$258.68	$258.70	$258.70
Purchase #4	$79.70	12.757%	$89.8673	$89.87	$89.85	$89.90
Purchase #5	$45.82	6.452%	$48.7763	$48.78	$48.80	$48.80
Purchase #6	$171.51	8.836%	$186.6646	$186.66	$186.65	$186.70
Purchase #7	$226.84	6.766%	$242.188	$242.19	$242.20	$242.20
7 purchase totals =	$1,026.47		$1,104.8489	$1,104.84	$1,104.85	$1,105.00