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	$177.59	9.487%	$194.438	$194.44	$194.45	$194.40
Purchase #2	$164.35	6.165%	$174.4822	$174.48	$174.50	$174.50
Purchase #3	$161.86	7.182%	$173.4848	$173.48	$173.50	$173.50
Purchase #4	$176.38	10.280%	$194.5119	$194.51	$194.50	$194.50
Purchase #5	$43.94	3.473%	$45.466	$45.47	$45.45	$45.50
Purchase #6	$122.30	12.112%	$137.113	$137.11	$137.10	$137.10
Purchase #7	$20.75	10.537%	$22.9364	$22.94	$22.95	$22.90
7 purchase totals =	$867.17		$942.4323	$942.43	$942.45	$942.40