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	$174.84	3.759%	$181.4122	$181.41	$181.40	$181.40
Purchase #2	$242.37	12.162%	$271.847	$271.85	$271.85	$271.80
Purchase #3	$112.67	4.256%	$117.4652	$117.47	$117.45	$117.50
Purchase #4	$19.27	10.273%	$21.2496	$21.25	$21.25	$21.20
Purchase #5	$54.38	12.728%	$61.3015	$61.30	$61.30	$61.30
Purchase #6	$147.67	7.838%	$159.2444	$159.24	$159.25	$159.20
Purchase #7	$82.72	8.241%	$89.537	$89.54	$89.55	$89.50
7 purchase totals =	$833.92		$902.0569	$902.06	$902.05	$901.90