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	$157.78	4.440%	$164.7854	$164.79	$164.80	$164.80
Purchase #2	$167.32	12.105%	$187.5741	$187.57	$187.55	$187.60
Purchase #3	$84.88	6.207%	$90.1485	$90.15	$90.15	$90.10
Purchase #4	$20.34	9.411%	$22.2542	$22.25	$22.25	$22.30
Purchase #5	$206.59	4.311%	$215.4961	$215.50	$215.50	$215.50
Purchase #6	$17.73	9.273%	$19.3741	$19.37	$19.35	$19.40
Purchase #7	$163.54	5.436%	$172.43	$172.43	$172.45	$172.40
7 purchase totals =	$818.18		$872.0624	$872.06	$872.05	$872.10