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	$165.52	13.669%	$188.1449	$188.14	$188.15	$188.10
Purchase #2	$61.90	7.439%	$66.5047	$66.50	$66.50	$66.50
Purchase #3	$117.75	13.814%	$134.016	$134.02	$134.00	$134.00
Purchase #4	$101.43	3.584%	$105.0653	$105.07	$105.05	$105.10
Purchase #5	$54.61	10.435%	$60.3086	$60.31	$60.30	$60.30
Purchase #6	$212.86	5.731%	$225.059	$225.06	$225.05	$225.10
Purchase #7	$187.93	6.249%	$199.6737	$199.67	$199.65	$199.70
7 purchase totals =	$902.00		$978.7722	$978.77	$978.70	$978.80