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	$102.77	9.307%	$112.3348	$112.33	$112.35	$112.30
Purchase #2	$54.97	11.298%	$61.1805	$61.18	$61.20	$61.20
Purchase #3	$35.51	10.615%	$39.2794	$39.28	$39.30	$39.30
Purchase #4	$171.81	10.739%	$190.2607	$190.26	$190.25	$190.30
Purchase #5	$59.30	4.670%	$62.0693	$62.07	$62.05	$62.10
Purchase #6	$224.60	7.573%	$241.609	$241.61	$241.60	$241.60
Purchase #7	$196.86	9.695%	$215.9456	$215.95	$215.95	$215.90
7 purchase totals =	$845.82		$922.6793	$922.68	$922.70	$922.70