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	$205.94	4.169%	$214.5256	$214.53	$214.55	$214.50
Purchase #2	$50.84	9.390%	$55.6139	$55.61	$55.60	$55.60
Purchase #3	$91.68	7.871%	$98.8961	$98.90	$98.90	$98.90
Purchase #4	$89.58	7.767%	$96.5377	$96.54	$96.55	$96.50
Purchase #5	$132.54	7.799%	$142.8768	$142.88	$142.90	$142.90
Purchase #6	$75.43	5.333%	$79.4527	$79.45	$79.45	$79.50
Purchase #7	$9.59	7.270%	$10.2872	$10.29	$10.30	$10.30
7 purchase totals =	$655.60		$698.1900	$698.20	$698.25	$698.20