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	$95.43	10.168%	$105.1333	$105.13	$105.15	$105.10
Purchase #2	$62.63	6.119%	$66.4623	$66.46	$66.45	$66.50
Purchase #3	$67.59	6.197%	$71.7786	$71.78	$71.80	$71.80
Purchase #4	$81.69	8.242%	$88.4229	$88.42	$88.40	$88.40
Purchase #5	$183.38	4.326%	$191.313	$191.31	$191.30	$191.30
Purchase #6	$56.43	12.451%	$63.4561	$63.46	$63.45	$63.50
Purchase #7	$19.27	10.610%	$21.3145	$21.31	$21.30	$21.30
7 purchase totals =	$566.42		$607.8807	$607.87	$607.85	$607.90