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	$177.36	5.725%	$187.5139	$187.51	$187.50	$187.50
Purchase #2	$41.39	12.792%	$46.6846	$46.68	$46.70	$46.70
Purchase #3	$89.39	3.819%	$92.8038	$92.80	$92.80	$92.80
Purchase #4	$76.51	3.795%	$79.4136	$79.41	$79.40	$79.40
Purchase #5	$169.78	9.229%	$185.449	$185.45	$185.45	$185.40
Purchase #6	$58.94	4.576%	$61.6371	$61.64	$61.65	$61.60
Purchase #7	$76.32	5.248%	$80.3253	$80.33	$80.35	$80.30
7 purchase totals =	$689.69		$733.8273	$733.82	$733.85	$733.70