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	$193.43	6.109%	$205.2466	$205.25	$205.25	$205.20
Purchase #2	$196.27	13.340%	$222.4524	$222.45	$222.45	$222.50
Purchase #3	$96.68	5.318%	$101.8214	$101.82	$101.80	$101.80
Purchase #4	$187.76	10.787%	$208.0137	$208.01	$208.00	$208.00
Purchase #5	$20.37	3.366%	$21.0557	$21.06	$21.05	$21.10
Purchase #6	$28.81	11.566%	$32.1422	$32.14	$32.15	$32.10
Purchase #7	$67.51	8.331%	$73.1343	$73.13	$73.15	$73.10
7 purchase totals =	$790.83		$863.8663	$863.86	$863.85	$863.80