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	$66.75	8.203%	$72.2255	$72.23	$72.25	$72.20
Purchase #2	$70.96	9.379%	$77.6153	$77.62	$77.60	$77.60
Purchase #3	$7.41	6.540%	$7.8946	$7.89	$7.90	$7.90
Purchase #4	$24.69	5.538%	$26.0573	$26.06	$26.05	$26.10
Purchase #5	$66.39	13.649%	$75.4516	$75.45	$75.45	$75.50
Purchase #6	$43.68	6.570%	$46.5498	$46.55	$46.55	$46.50
Purchase #7	$105.62	5.781%	$111.7259	$111.73	$111.75	$111.70
7 purchase totals =	$385.50		$417.5200	$417.53	$417.55	$417.50