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	$120.39	10.256%	$132.7372	$132.74	$132.75	$132.70
Purchase #2	$46.45	5.322%	$48.9221	$48.92	$48.90	$48.90
Purchase #3	$229.55	6.424%	$244.2963	$244.30	$244.30	$244.30
Purchase #4	$136.72	3.326%	$141.2673	$141.27	$141.25	$141.30
Purchase #5	$212.85	5.268%	$224.0629	$224.06	$224.05	$224.10
Purchase #6	$173.31	3.196%	$178.849	$178.85	$178.85	$178.80
Purchase #7	$89.43	11.457%	$99.676	$99.68	$99.70	$99.70
7 purchase totals =	$1,008.70		$1,069.8108	$1,069.82	$1,069.80	$1,069.80