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	$22.91	11.678%	$25.5854	$25.59	$25.60	$25.60
Purchase #2	$12.98	7.673%	$13.976	$13.98	$14.00	$14.00
Purchase #3	$139.59	13.836%	$158.9037	$158.90	$158.90	$158.90
Purchase #4	$71.38	9.842%	$78.4052	$78.41	$78.40	$78.40
Purchase #5	$162.44	11.331%	$180.8461	$180.85	$180.85	$180.80
Purchase #6	$140.81	7.644%	$151.5735	$151.57	$151.55	$151.60
Purchase #7	$50.37	5.285%	$53.0321	$53.03	$53.05	$53.00
7 purchase totals =	$600.48		$662.3220	$662.33	$662.35	$662.30