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	$171.47	7.363%	$184.0953	$184.10	$184.10	$184.10
Purchase #2	$155.39	8.138%	$168.0356	$168.04	$168.05	$168.00
Purchase #3	$165.60	7.763%	$178.4555	$178.46	$178.45	$178.50
Purchase #4	$66.64	10.404%	$73.5732	$73.57	$73.55	$73.60
Purchase #5	$188.77	5.564%	$199.2732	$199.27	$199.25	$199.30
Purchase #6	$67.89	6.686%	$72.4291	$72.43	$72.45	$72.40
Purchase #7	$101.26	6.504%	$107.846	$107.85	$107.85	$107.80
7 purchase totals =	$917.02		$983.7079	$983.72	$983.70	$983.70