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	$239.38	5.502%	$252.5507	$252.55	$252.55	$252.60
Purchase #2	$94.98	6.143%	$100.8146	$100.81	$100.80	$100.80
Purchase #3	$39.86	9.839%	$43.7818	$43.78	$43.80	$43.80
Purchase #4	$239.33	7.112%	$256.3511	$256.35	$256.35	$256.40
Purchase #5	$199.71	4.846%	$209.3879	$209.39	$209.40	$209.40
Purchase #6	$122.56	12.152%	$137.4535	$137.45	$137.45	$137.50
Purchase #7	$17.88	6.366%	$19.0182	$19.02	$19.00	$19.00
7 purchase totals =	$953.70		$1,019.3578	$1,019.35	$1,019.35	$1,019.50