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	$144.86	9.442%	$158.5377	$158.54	$158.55	$158.50
Purchase #2	$40.82	5.559%	$43.0892	$43.09	$43.10	$43.10
Purchase #3	$235.26	5.682%	$248.6275	$248.63	$248.65	$248.60
Purchase #4	$189.83	4.845%	$199.0273	$199.03	$199.05	$199.00
Purchase #5	$39.50	7.170%	$42.3322	$42.33	$42.35	$42.30
Purchase #6	$70.45	5.112%	$74.0514	$74.05	$74.05	$74.10
Purchase #7	$57.29	3.154%	$59.0969	$59.10	$59.10	$59.10
7 purchase totals =	$778.01		$824.7622	$824.77	$824.85	$824.70