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	$62.26	5.700%	$65.8088	$65.81	$65.80	$65.80
Purchase #2	$56.46	10.667%	$62.4826	$62.48	$62.50	$62.50
Purchase #3	$12.69	8.302%	$13.7435	$13.74	$13.75	$13.70
Purchase #4	$134.78	9.114%	$147.0638	$147.06	$147.05	$147.10
Purchase #5	$153.58	9.210%	$167.7247	$167.72	$167.70	$167.70
Purchase #6	$104.26	6.669%	$111.2131	$111.21	$111.20	$111.20
Purchase #7	$101.61	10.661%	$112.4426	$112.44	$112.45	$112.40
7 purchase totals =	$625.64		$680.4791	$680.46	$680.45	$680.40